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Displaying entries 1-50 of 77.
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EC | 1.1.1.34 | ||||||||||||||||||
Accepted name: | hydroxymethylglutaryl-CoA reductase (NADPH) | ||||||||||||||||||
Reaction: | (R)-mevalonate + CoA + 2 NADP+ = (S)-3-hydroxy-3-methylglutaryl-CoA + 2 NADPH + 2 H+ | ||||||||||||||||||
For diagram of mevalonate biosynthesis, click here | |||||||||||||||||||
Other name(s): | hydroxymethylglutaryl coenzyme A reductase (reduced nicotinamide adenine dinucleotide phosphate); 3-hydroxy-3-methylglutaryl-CoA reductase (ambiguous); β-hydroxy-β-methylglutaryl coenzyme A reductase (ambiguous); hydroxymethylglutaryl CoA reductase (NADPH); S-3-hydroxy-3-methylglutaryl-CoA reductase (ambiguous); NADPH-hydroxymethylglutaryl-CoA reductase; HMGCoA reductase-mevalonate:NADP-oxidoreductase (acetylating-CoA); 3-hydroxy-3-methylglutaryl CoA reductase (NADPH); hydroxymethylglutaryl-CoA reductase (NADPH2) | ||||||||||||||||||
Systematic name: | (R)-mevalonate:NADP+ oxidoreductase (CoA-acylating) | ||||||||||||||||||
Comments: | The enzyme is inactivated by EC 2.7.11.31 {[hydroxymethylglutaryl-CoA reductase (NADPH)] kinase} and reactivated by EC 3.1.3.47 {[hydroxymethylglutaryl-CoA reductase (NADPH)]-phosphatase}. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9028-35-7 | ||||||||||||||||||
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EC | 1.1.1.52 | ||||||||||||||||||
Accepted name: | 3α-hydroxycholanate dehydrogenase (NAD+) | ||||||||||||||||||
Reaction: | lithocholate + NAD+ = 3-oxo-5β-cholan-24-oate + NADH + H+ | ||||||||||||||||||
For diagram of cholesterol catabolism (rings A, B and C), click here | |||||||||||||||||||
Glossary: | lithocholate = 3α-hydroxy-5β-cholan-24-oate | ||||||||||||||||||
Other name(s): | α-hydroxy-cholanate dehydrogenase; lithocholate:NAD+ oxidoreductase; 3α-hydroxycholanate dehydrogenase | ||||||||||||||||||
Systematic name: | lithocholate:NAD+ 3-oxidoreductase | ||||||||||||||||||
Comments: | Also acts on other 3α-hydroxysteroids with an acidic side-chain. cf. EC 1.1.1.392, 3α-hydroxycholanate dehydrogenase (NADP+). | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9028-57-3 | ||||||||||||||||||
References: |
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EC | 1.1.1.62 | ||||||||||||||||||
Accepted name: | 17β-estradiol 17-dehydrogenase | ||||||||||||||||||
Reaction: | 17β-estradiol + NAD(P)+ = estrone + NAD(P)H + H+ | ||||||||||||||||||
Other name(s): | 20α-hydroxysteroid dehydrogenase; 17β,20α-hydroxysteroid dehydrogenase; 17β-estradiol dehydrogenase; estradiol dehydrogenase; estrogen 17-oxidoreductase; 17β-HSD; HSD17B7 | ||||||||||||||||||
Systematic name: | 17β-estradiol:NAD(P)+ 17-oxidoreductase | ||||||||||||||||||
Comments: | The enzyme oxidizes or reduces the hydroxy/keto group on C17 of estrogens and androgens in mammals and regulates the biological potency of these steroids. The mammalian enzyme is bifunctional and also catalyses EC 1.1.1.270, 3β-hydroxysteroid 3-dehydrogenase [3]. The enzyme also acts on (S)-20-hydroxypregn-4-en-3-one and related compounds, oxidizing the (S)-20-group, but unlike EC 1.1.1.149, 20α-hydroxysteroid dehydrogenase, it is Si-specific with respect to NAD(P)+. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, GTD, KEGG, MetaCyc, PDB, CAS registry number: 9028-61-9 | ||||||||||||||||||
References: |
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EC | 1.1.1.145 | ||||||||||||||||||
Accepted name: | 3β-hydroxy-Δ5-steroid dehydrogenase | ||||||||||||||||||
Reaction: | a 3β-hydroxy-Δ5-steroid + NAD+ = a 3-oxo-Δ5-steroid + NADH + H+ | ||||||||||||||||||
For diagram of cholesterol catabolism (rings a, B and c), click here | |||||||||||||||||||
Other name(s): | progesterone reductase; Δ5-3β-hydroxysteroid dehydrogenase; 3β-hydroxy-5-ene steroid dehydrogenase; 3β-hydroxy steroid dehydrogenase/isomerase; 3β-hydroxy-Δ5-C27-steroid dehydrogenase/isomerase; 3β-hydroxy-Δ5-C27-steroid oxidoreductase; 3β-hydroxy-5-ene-steroid oxidoreductase; steroid-Δ5-3β-ol dehydrogenase; 3β-HSDH; 5-ene-3-β-hydroxysteroid dehydrogenase; 3β-hydroxy-5-ene-steroid dehydrogenase | ||||||||||||||||||
Systematic name: | 3β-hydroxy-Δ5-steroid:NAD+ 3-oxidoreductase | ||||||||||||||||||
Comments: | This activity is found in several bifunctional enzymes that catalyse the oxidative conversion of Δ5-3-hydroxy steroids to a Δ4-3-oxo configuration. This conversion is carried out in two separate, sequential reactions; in the first reaction, which requires NAD+, the enzyme catalyses the dehydrogenation of the 3β-hydroxy steroid to a 3-oxo intermediate. In the second reaction the reduced cosubstrate, which remains attached to the enzyme, activates the isomerization of the Δ5 form to a Δ4 form (cf. EC 5.3.3.1, steroid Δ-isomerase). Substrates include dehydroepiandrosterone (which is converted into androst-5-ene-3,17-dione), pregnenolone (converted to progesterone) and cholest-5-en-3-one, an intermediate of cholesterol degradation. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9044-85-3 | ||||||||||||||||||
References: |
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EC | 1.1.1.170 | ||||||||||||||||||
Accepted name: | 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating) | ||||||||||||||||||
Reaction: | a 3β-hydroxysteroid-4α-carboxylate + NAD(P)+ = a 3-oxosteroid + CO2 + NAD(P)H | ||||||||||||||||||
For diagram of sterol ring A modification, click here | |||||||||||||||||||
Other name(s): | 3β-hydroxy-4β-methylcholestenecarboxylate 3-dehydrogenase (decarboxylating); 3β-hydroxy-4β-methylcholestenoate dehydrogenase; sterol 4α-carboxylic decarboxylase; sterol-4α-carboxylate 3-dehydrogenase (decarboxylating) (ambiguous); ERG26 (gene name); NSDHL (gene name) | ||||||||||||||||||
Systematic name: | 3β-hydroxysteroid-4α-carboxylate:NAD(P)+ 3-oxidoreductase (decarboxylating) | ||||||||||||||||||
Comments: | The enzyme participates in the biosynthesis of several important sterols such as ergosterol and cholesterol. It is part of a three enzyme system that removes methyl groups from the C-4 position of steroid molecules. The first enzyme, EC 1.14.18.9, 4α-methylsterol monooxygenase, catalyses three successive oxidations of the methyl group, resulting in a carboxyl group; the second enzyme, EC 1.1.1.170, catalyses an oxidative decarboxylation that results in a reduction of the 3β-hydroxy group at the C-3 carbon to an oxo group; and the last enzyme, EC 1.1.1.270, 3β-hydroxysteroid 3-dehydrogenase, reduces the 3-oxo group back to a 3β-hydroxyl. If a second methyl group remains at the C-4 position, this enzyme also catalyses its epimerization from 4β to 4α orientation, so it could serve as a substrate for a second round of demethylation. cf. EC 1.1.1.418, plant 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating). | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 71822-23-6 | ||||||||||||||||||
References: |
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EC | 1.1.1.181 | ||||||||||||||||||
Accepted name: | cholest-5-ene-3β,7α-diol 3β-dehydrogenase | ||||||||||||||||||
Reaction: | cholest-5-ene-3β,7α-diol + NAD+ = 7α-hydroxycholest-4-en-3-one + NADH + H+ | ||||||||||||||||||
For diagram of cholesterol catabolism (rings A, B and C), click here | |||||||||||||||||||
Other name(s): | 3β-hydroxy-Δ5-C27-steroid oxidoreductase (ambiguous) | ||||||||||||||||||
Systematic name: | cholest-5-ene-3β,7α-diol:NAD+ 3-oxidoreductase | ||||||||||||||||||
Comments: | Highly specific for 3β,7α-dihydroxy-C27-steroids with Δ5-double bond. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 56626-16-5 | ||||||||||||||||||
References: |
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EC | 1.1.1.270 | ||||||||||||||||||
Accepted name: | 3β-hydroxysteroid 3-dehydrogenase | ||||||||||||||||||
Reaction: | a 3β-hydroxysteroid + NADP+ = a 3-oxosteroid + NADPH + H+ | ||||||||||||||||||
For diagram of sterol ring A modification, click here | |||||||||||||||||||
Other name(s): | 3-keto-steroid reductase; 3-KSR; HSD17B7 (gene name); ERG27 (gene name) | ||||||||||||||||||
Systematic name: | 3β-hydroxysteroid:NADP+ 3-oxidoreductase | ||||||||||||||||||
Comments: | The enzyme acts on multiple 3β-hydroxysteroids. Participates in the biosynthesis of zemosterol and cholesterol, where it catalyses the reaction in the opposite direction to that shown. The mammalian enzyme is bifunctional and also catalyses EC 1.1.1.62, 17β-estradiol 17-dehydrogenase [4]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 42616-29-5 | ||||||||||||||||||
References: |
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EC | 1.1.3.6 | ||||||||||||||||||
Accepted name: | cholesterol oxidase | ||||||||||||||||||
Reaction: | cholesterol + O2 = cholest-5-en-3-one + H2O2 | ||||||||||||||||||
For diagram of cholesterol catabolism (rings A, B and C), click here | |||||||||||||||||||
Other name(s): | cholesterol- O2 oxidoreductase; 3β-hydroxy steroid oxidoreductase; 3β-hydroxysteroid:oxygen oxidoreductase | ||||||||||||||||||
Systematic name: | cholesterol:oxygen oxidoreductase | ||||||||||||||||||
Comments: | Contains FAD. Cholesterol oxidases are secreted bacterial bifunctional enzymes that catalyse the first two steps in the degradation of cholesterol. The enzyme catalyses the oxidation of the 3β-hydroxyl group to a keto group, and the isomerization of the double bond in the oxidized steroid ring system from the Δ5 position to Δ6 position (cf. EC 5.3.3.1, steroid Δ-isomerase). | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9028-76-6 | ||||||||||||||||||
References: |
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EC | 1.3.1.3 | ||||||||||||||||||
Accepted name: | Δ4-3-oxosteroid 5β-reductase | ||||||||||||||||||
Reaction: | a 3-oxo-5β-steroid + NADP+ = a 3-oxo-Δ4-steroid + NADPH + H+ | ||||||||||||||||||
For diagram of cholesterol catabolism (rings a, B and c), click here | |||||||||||||||||||
Other name(s): | 3-oxo-Δ4-steroid 5β-reductase; 5β-reductase; androstenedione 5β-reductase; cholestenone 5β-reductase; cortisone 5β-reductase; cortisone β-reductase; cortisone Δ4-5β-reductase; steroid 5β-reductase; testosterone 5β-reductase; Δ4-3-ketosteroid 5β-reductase; Δ4-5β-reductase; Δ4-hydrogenase; 4,5β-dihydrocortisone:NADP+ Δ4-oxidoreductase; 3-oxo-5β-steroid:NADP+ Δ4-oxidoreductase; 5β-cholestan-3-one:NADP+ 4,5-oxidoreductase | ||||||||||||||||||
Systematic name: | 3-oxo-5β-steroid:NADP+ 4,5-oxidoreductase | ||||||||||||||||||
Comments: | The enzyme from human efficiently catalyses the reduction of progesterone, androstenedione, 17α-hydroxyprogesterone and testosterone to 5β-reduced metabolites; it can also act on aldosterone, corticosterone and cortisol, but to a lesser extent [8]. The bile acid intermediates 7α,12α-dihydroxy-4-cholesten-3-one and 7α-hydroxy-4-cholesten-3-one can also act as substrates [9]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9029-08-7 | ||||||||||||||||||
References: |
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EC | 1.3.1.21 | ||||||||||||||||||
Accepted name: | 7-dehydrocholesterol reductase | ||||||||||||||||||
Reaction: | cholesterol + NADP+ = cholesta-5,7-dien-3β-ol + NADPH + H+ | ||||||||||||||||||
For diagram of sterol ring b, c, D modification, click here | |||||||||||||||||||
Other name(s): | DHCR7 (gene name); 7-DHC reductase; 7-dehydrocholesterol dehydrogenase/cholesterol oxidase; Δ7-sterol reductase | ||||||||||||||||||
Systematic name: | cholesterol:NADP+ Δ7-oxidoreductase | ||||||||||||||||||
Comments: | The enzyme is part of the cholesterol biosynthesis pathway. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9080-21-1 | ||||||||||||||||||
References: |
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EC | 1.3.1.70 | ||||||||||||||||||
Accepted name: | Δ14-sterol reductase | ||||||||||||||||||
Reaction: | 4,4-dimethyl-5α-cholesta-8,24-dien-3β-ol + NADP+ = 4,4-dimethyl-5α-cholesta-8,14,24-trien-3β-ol + NADPH + H+ | ||||||||||||||||||
For diagram of the modification of sterol rings B, C and D, click here | |||||||||||||||||||
Systematic name: | 4,4-dimethyl-5α-cholesta-8,24-dien-3β-ol:NADP+ Δ14-oxidoreductase | ||||||||||||||||||
Comments: | This enzyme acts on a range of steroids with a 14(15)-double bond. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 69403-07-2 | ||||||||||||||||||
References: |
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EC | 1.3.1.72 | ||||||||||||||||||
Accepted name: | Δ24-sterol reductase | ||||||||||||||||||
Reaction: | 5α-cholest-7-en-3β-ol + NADP+ = 5α-cholesta-7,24-dien-3β-ol + NADPH + H+ | ||||||||||||||||||
For diagram of sterol-sidechain modification, click here | |||||||||||||||||||
Glossary: | desmosterol = cholesta-5,24-dien-3β-ol lanosterol = 4,4,14-trimethyl-5α-cholesta-8,24-dien-3β-ol zymostrol = 5α-cholesta-8,24-dien-3β-ol |
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Other name(s): | lanosterol Δ24-reductase | ||||||||||||||||||
Systematic name: | sterol:NADP+ Δ24-oxidoreductase | ||||||||||||||||||
Comments: | Acts on a range of steroids with a 24(25)-double bond, including lanosterol, desmosterol and zymosterol. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 9033-57-2 | ||||||||||||||||||
References: |
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EC | 1.14.1.9 | ||||||||||||||||||
Deleted entry: | cholesterol 20-hydroxylase | ||||||||||||||||||
EC | 1.14.13.15 | ||||||||||||||||||
Transferred entry: | cholestanetriol 26-monooxygenase. Now EC 1.14.15.15, cholestanetriol 26-monooxygenase. | ||||||||||||||||||
EC | 1.14.13.17 | ||||||||||||||||||
Transferred entry: | cholesterol 7α-monooxygenase. Now EC 1.14.14.23, cholesterol 7α-monooxygenase | ||||||||||||||||||
EC | 1.14.13.60 | ||||||||||||||||||
Transferred entry: | 27-hydroxycholesterol 7α-monooxygenase. Now classified as EC 1.14.14.29, 25/26-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
EC | 1.14.13.70 | ||||||||||||||||||
Transferred entry: | sterol 14α-demethylase. Now EC 1.14.14.154, sterol 14α-demethylase | ||||||||||||||||||
EC | 1.14.13.72 | ||||||||||||||||||
Transferred entry: | methylsterol monooxygenase. Now classified as EC 1.14.18.9, methylsterol monooxygenase | ||||||||||||||||||
EC | 1.14.13.95 | ||||||||||||||||||
Transferred entry: | 7α-hydroxycholest-4-en-3-one 12α-hydroxylase. Now included with EC 1.14.14.139, 5β-cholestane-3α,7α-diol 12α-hydroxylase | ||||||||||||||||||
EC | 1.14.13.96 | ||||||||||||||||||
Transferred entry: | 5β-cholestane-3α,7α-diol 12α-hydroxylase. Now EC 1.14.14.139, 5β-cholestane-3α,7α-diol 12α-hydroxylase | ||||||||||||||||||
EC | 1.14.13.98 | ||||||||||||||||||
Transferred entry: | cholesterol 24-hydroxylase. Now EC 1.14.14.25, cholesterol 24-hydroxylase | ||||||||||||||||||
EC | 1.14.13.99 | ||||||||||||||||||
Transferred entry: | 24-hydroxycholesterol 7α-hydroxylase. Now EC 1.14.14.26, 24-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
EC | 1.14.13.100 | ||||||||||||||||||
Transferred entry: | 25/26-hydroxycholesterol 7α-hydroxylase. Now classified as EC 1.14.14.29, 25/26-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
EC | 1.14.13.132 | ||||||||||||||||||
Transferred entry: | squalene monooxygenase. Now EC 1.14.14.17, squalene monooxygenase | ||||||||||||||||||
EC | 1.14.13.141 | ||||||||||||||||||
Transferred entry: | cholest-4-en-3-one 26-monooxygenase [(25S)-3-oxocholest-4-en-26-oate forming]. Now EC 1.14.15.29, cholest-4-en-3-one 26-monooxygenase [(25S)-3-oxocholest-4-en-26-oate forming].. | ||||||||||||||||||
EC | 1.14.13.142 | ||||||||||||||||||
Transferred entry: | 3-ketosteroid 9α-monooxygenase. Now EC 1.14.15.30, 3-ketosteroid 9α-monooxygenase | ||||||||||||||||||
EC | 1.14.13.221 | ||||||||||||||||||
Transferred entry: | cholest-4-en-3-one 26-monooxygenase [(25R)-3-oxocholest-4-en-26-oate forming]. Now EC 1.14.15.28, cholest-4-en-3-one 26-monooxygenase [(25R)-3-oxocholest-4-en-26-oate forming] | ||||||||||||||||||
EC | 1.14.14.12 | ||||||||||||||||||
Accepted name: | 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione monooxygenase | ||||||||||||||||||
Reaction: | 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione + FMNH2 + O2 = 3,4-dihydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione + FMN + H2O | ||||||||||||||||||
Other name(s): | HsaA | ||||||||||||||||||
Systematic name: | 3-hydroxy-9,10-secoandrosta-1,3,5(10)-triene-9,17-dione,FMNH2:oxygen oxidoreductase | ||||||||||||||||||
Comments: | This bacterial enzyme participates in the degradation of several steroids, including cholesterol and testosterone. It can use either FADH or FMNH2 as flavin cofactor. The enzyme forms a two-component system with a reductase (HsaB) that utilizes NADH to reduce the flavin, which is then transferred to the oxygenase subunit. | ||||||||||||||||||
Links to other databases: | BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.14.17 | ||||||||||||||||||
Accepted name: | squalene monooxygenase | ||||||||||||||||||
Reaction: | squalene + [reduced NADPH—hemoprotein reductase] + O2 = (3S)-2,3-epoxy-2,3-dihydrosqualene + [oxidized NADPH—hemoprotein reductase] + H2O | ||||||||||||||||||
For diagram of α-onocerin biosynthesis, click here and for diagram of triterpenoid biosynthesis, click here | |||||||||||||||||||
Other name(s): | squalene epoxidase; squalene-2,3-epoxide cyclase; squalene 2,3-oxidocyclase; squalene hydroxylase; squalene oxydocyclase; squalene-2,3-epoxidase | ||||||||||||||||||
Systematic name: | squalene,NADPH—hemoprotein:oxygen oxidoreductase (2,3-epoxidizing) | ||||||||||||||||||
Comments: | A flavoprotein (FAD). This enzyme, together with EC 5.4.99.7, lanosterol synthase, was formerly known as squalene oxidocyclase. The electron donor is EC 1.6.2.4, NADPH—hemoprotein reductase [5,7]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9029-62-3 | ||||||||||||||||||
References: |
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EC | 1.14.14.23 | ||||||||||||||||||
Accepted name: | cholesterol 7α-monooxygenase | ||||||||||||||||||
Reaction: | cholesterol + [reduced NADPH—hemoprotein reductase] + O2 = 7α-hydroxycholesterol + [oxidized NADPH—hemoprotein reductase] + H2O | ||||||||||||||||||
For diagram of cholesterol catabolism (rings A, B and C), click here | |||||||||||||||||||
Other name(s): | cholesterol 7α-hydroxylase; CYP7A1 (gene name) | ||||||||||||||||||
Systematic name: | cholesterol,NADPH—hemoprotein reductase:oxygen oxidoreductase (7α-hydroxylating) | ||||||||||||||||||
Comments: | A P-450 heme-thiolate liver protein that catalyses the first step in the biosynthesis of bile acids. The direct electron donor to the enzyme is EC 1.6.2.4, NADPH—hemoprotein reductase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9037-53-0 | ||||||||||||||||||
References: |
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EC | 1.14.14.25 | ||||||||||||||||||
Accepted name: | cholesterol 24-hydroxylase | ||||||||||||||||||
Reaction: | cholesterol + [reduced NADPH—hemoprotein reductase] + O2 = (24S)-cholest-5-ene-3β,24-diol + [oxidized NADPH—hemoprotein reductase] + H2O | ||||||||||||||||||
For diagram of cholic acid biosynthesis (sidechain), click here | |||||||||||||||||||
Glossary: | cholesterol = cholest-5-en-3β-ol (24S)-24-hydroxycholesterol = (24S)-cholest-5-ene-3β,24-diol |
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Other name(s): | cholesterol 24-monooxygenase; CYP46; CYP46A1; cholesterol 24S-hydroxylase; cytochrome P450 46A1 | ||||||||||||||||||
Systematic name: | cholesterol,NADPH—hemoprotein reductase:oxygen oxidoreductase (24-hydroxylating) | ||||||||||||||||||
Comments: | A P-450 heme-thiolate protein. The enzyme can also produce 25-hydroxycholesterol. In addition, it can further hydroxylate the product to 24,25-dihydroxycholesterol and 24,27-dihydroxycholesterol [2]. This reaction is the first step in the enzymic degradation of cholesterol in the brain as hydroxycholesterol can pass the blood—brain barrier whereas cholesterol cannot [3]. The direct electron donor to the enzyme is EC 1.6.2.4, NADPH—hemoprotein reductase [3]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 50812-30-1, 213327-78-7 | ||||||||||||||||||
References: |
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EC | 1.14.14.26 | ||||||||||||||||||
Accepted name: | 24-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
Reaction: | (24S)-cholest-5-ene-3β,24-diol + [reduced NADPH—hemoprotein reductase] + O2 = (24S)-cholest-5-ene-3β,7α,24-triol + [oxidized NADPH—hemoprotein reductase] + H2O | ||||||||||||||||||
For diagram of cholesterol catabolism (rings a, B and c), click here | |||||||||||||||||||
Glossary: | (24S)-cholest-5-ene-3β,24-diol = (24S)-24-hydroxycholesterol | ||||||||||||||||||
Other name(s): | 24-hydroxycholesterol 7α-monooxygenase; CYP39A1; CYP39A1 oxysterol 7α-hydroxylase | ||||||||||||||||||
Systematic name: | (24S)-cholest-5-ene-3β,24-diol,NADPH—hemoprotein reductase:oxygen oxidoreductase (7α-hydroxylating) | ||||||||||||||||||
Comments: | A P-450 heme-thiolate protein that is found in liver microsomes and in ciliary non-pigmented epithelium [2]. The enzyme is specific for (24S)-cholest-5-ene-3β,24-diol, which is formed mostly in the brain by EC 1.14.14.25, cholesterol 24-hydroxylase. The direct electron donor to the enzyme is EC 1.6.2.4, NADPH—hemoprotein reductase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 288309-90-0 | ||||||||||||||||||
References: |
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EC | 1.14.14.29 | ||||||||||||||||||
Accepted name: | 25/26-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
Reaction: | (1) cholest-5-ene-3β,25-diol + [reduced NADPH—hemoprotein reductase] + O2 = cholest-5-ene-3β,7α,25-triol + [oxidized NADPH—hemoprotein reductase] + H2O (2) (25R)-cholest-5-ene-3β,26-diol + [reduced NADPH—hemoprotein reductase] + O2 = (25R)-cholest-5-ene-3β,7α,26-triol + [oxidized NADPH—hemoprotein reductase] + H2O |
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For diagram of cholesterol catabolism (rings a, B and c), click here | |||||||||||||||||||
Other name(s): | 25-hydroxycholesterol 7α-monooxygenase; CYP7B1; CYP7B1 oxysterol 7α-hydroxylase; 27-hydroxycholesterol 7-monooxygenase; 27-hydroxycholesterol 7α-hydroxylase; cholest-5-ene-3β,25-diol,NADPH:oxygen oxidoreductase (7α-hydroxylating); 25-hydroxycholesterol 7α-hydroxylase | ||||||||||||||||||
Systematic name: | cholest-5-ene-3β,25/26-diol,[NADPH—hemoprotein reductase]:oxygen oxidoreductase (7α-hydroxylating) | ||||||||||||||||||
Comments: | A P-450 (heme-thiolate) protein. Unlike EC 1.14.14.26, 24-hydroxycholesterol 7α-monooxygenase, which is specific for its oxysterol substrate, this enzyme can also metabolize the oxysterols 24,25-epoxycholesterol, 22-hydroxycholesterol and 24-hydroxycholesterol, but to a lesser extent [2]. The direct electron donor to the enzyme is EC 1.6.2.4, NADPH—hemoprotein reductase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 149316-80-3 | ||||||||||||||||||
References: |
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EC | 1.14.14.46 | ||||||||||||||||||
Accepted name: | pimeloyl-[acyl-carrier protein] synthase | ||||||||||||||||||
Reaction: | a long-chain acyl-[acyl-carrier protein] + 2 reduced flavodoxin + 3 O2 = pimeloyl-[acyl-carrier protein] + an n-alkanal + 2 oxidized flavodoxin + 3 H2O (overall reaction) (1a) a long-chain acyl-[acyl-carrier protein] + reduced flavodoxin + O2 = a (7S)-7-hydroxy-long-chain-acyl-[acyl-carrier protein] + oxidized flavodoxin + H2O (1b) a (7S)-7-hydroxy-long-chain-acyl-[acyl-carrier protein] + reduced flavodoxin + O2 = a (7R,8R)-7,8-dihydroxy-long-chain-acyl-[acyl-carrier protein] + oxidized flavodoxin + H2O (1c) a (7R,8R)-7,8-dihydroxy-long-chain-acyl-[acyl-carrier protein] + reduced flavodoxin + O2 = a 7-oxoheptanoyl-[acyl-carrier protein] + an n-alkanal + oxidized flavodoxin + 2 H2O (1d) a 7-oxoheptanoyl-[acyl-carrier protein] + oxidized flavodoxin + H2O = a pimeloyl-[acyl-carrier protein] + reduced flavodoxin + H+ |
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Glossary: | a long-chain acyl-[acyl-carrier protein] = an acyl-[acyl-carrier protein] thioester where the acyl chain contains 13 to 22 carbon atoms. palmitoyl-[acyl-carrier protein] = hexadecanoyl-[acyl-carrier protein] pimeloyl-[acyl-carrier protein] = 6-carboxyhexanoyl-[acyl-carrier protein] |
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Other name(s): | bioI (gene name); P450BioI; CYP107H1 | ||||||||||||||||||
Systematic name: | acyl-[acyl-carrier protein],reduced-flavodoxin:oxygen oxidoreductase (pimeloyl-[acyl-carrier protein]-forming) | ||||||||||||||||||
Comments: | A cytochrome P-450 (heme-thiolate) protein. The enzyme catalyses an oxidative C-C bond cleavage of long-chain acyl-[acyl-carrier protein]s of various lengths to generate pimeloyl-[acyl-carrier protein], an intermediate in the biosynthesis of biotin. The preferred substrate of the enzyme from the bacterium Bacillus subtilis is palmitoyl-[acyl-carrier protein] which then gives heptanal as the alkanal. The mechanism is similar to EC 1.14.15.6, cholesterol monooxygenase (side-chain-cleaving), followed by a hydroxylation step, which may occur spontaneously [2]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.14.139 | ||||||||||||||||||
Accepted name: | 5β-cholestane-3α,7α-diol 12α-hydroxylase | ||||||||||||||||||
Reaction: | (1) 5β-cholestane-3α,7α-diol + [reduced NADPH—hemoprotein reductase] + O2 = 5β-cholestane-3α,7α,12α-triol + [oxidized NADPH—hemoprotein reductase] + H2O (2) 7α-hydroxycholest-4-en-3-one + [reduced NADPH—hemoprotein reductase] + O2 = 7α,12α-dihydroxycholest-4-en-3-one + [oxidized NADPH—hemoprotein reductase] + H2O (3) chenodeoxycholate + [reduced NADPH—hemoprotein reductase] + O2 = cholate + [oxidized NADPH—hemoprotein reductase] + H2O |
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For diagram of cholesterol catabolism (rings A, B and C), click here | |||||||||||||||||||
Glossary: | chenodeoxycholate = 3α,7α-dihydroxy-5β-cholan-24-oate cholate = 3α,7α-12α-trihydroxy-5β-cholan-24-oate |
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Other name(s): | 5β-cholestane-3α,7α-diol 12α-monooxygenase; sterol 12α-hydroxylase (ambiguous); CYP8B1; cytochrome P450 8B1; 7α-hydroxycholest-4-en-3-one 12α-hydroxylase; 7α-hydroxy-4-cholesten-3-one 12α-monooxygenase; chenodeoxycholate 12α monooxygenase | ||||||||||||||||||
Systematic name: | 5β-cholestane-3α,7α-diol,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (12α-hydroxylating) | ||||||||||||||||||
Comments: | A cytochrome P-450 (heme-thiolate) protein found in mammals. This is the key enzyme in the biosynthesis of the bile acid cholate. The enzyme can also hydroxylate 5β-cholestane-3α,7α-diol at the 25 and 26 position, but to a lesser extent [2]. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.14.154 | ||||||||||||||||||
Accepted name: | sterol 14α-demethylase | ||||||||||||||||||
Reaction: | a 14α-methylsteroid + 3 [reduced NADPH—hemoprotein reductase] + 3 O2 = a Δ14-steroid + formate + 3 [oxidized NADPH—hemoprotein reductase] + 4 H2O (overall reaction) (1a) a 14α-methylsteroid + [reduced NADPH—hemoprotein reductase] + O2 = a 14α-hydroxymethylsteroid + [oxidized NADPH—hemoprotein reductase] + H2O (1b) a 14α-hydroxysteroid + [reduced NADPH—hemoprotein reductase] + O2 = a 14α-formylsteroid + [oxidized NADPH—hemoprotein reductase] + 2 H2O (1c) a 14α-formylsteroid + [reduced NADPH—hemoprotein reductase] + O2 = a Δ14-steroid + formate + [oxidized NADPH—hemoprotein reductase] + H2O |
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For diagram of sterol ring B, C, D modification, click here | |||||||||||||||||||
Glossary: | obtusifoliol = 4α,14α-dimethyl-5α-ergosta-8,24(28)-dien-3β-ol or 4α,14α-dimethyl-24-methylene-5α-cholesta-8-en-3β-ol | ||||||||||||||||||
Other name(s): | obtusufoliol 14-demethylase; lanosterol 14-demethylase; lanosterol 14α-demethylase; sterol 14-demethylase; CYP51 (gene name); ERG11 (gene name) | ||||||||||||||||||
Systematic name: | sterol,[reduced NADPH—hemoprotein reductase]:oxygen oxidoreductase (14-methyl cleaving) | ||||||||||||||||||
Comments: | This cytochrome P-450 (heme-thiolate) enzyme acts on a range of steroids with a 14α-methyl group, such as obtusifoliol and lanosterol. The enzyme catalyses a hydroxylation and a reduction of the 14α-methyl group, followed by a second hydroxylation, resulting in the elimination of formate and formation of a 14(15) double bond. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 60063-87-8 | ||||||||||||||||||
References: |
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EC | 1.14.15.6 | ||||||||||||||||||
Accepted name: | cholesterol monooxygenase (side-chain-cleaving) | ||||||||||||||||||
Reaction: | cholesterol + 6 reduced adrenodoxin + 3 O2 + 6 H+ = pregnenolone + 4-methylpentanal + 6 oxidized adrenodoxin + 4 H2O (overall reaction) (1a) cholesterol + 2 reduced adrenodoxin + O2 + 2 H+ = (22R)-22-hydroxycholesterol + 2 oxidized adrenodoxin + H2O (1b) (22R)-22-hydroxycholesterol + 2 reduced adrenodoxin + O2 + 2 H+ = (20R,22R)-20,22-dihydroxycholesterol + 2 oxidized adrenodoxin + H2O (1c) (20R,22R)-20,22-dihydroxy-cholesterol + 2 reduced adrenodoxin + O2 + 2 H+ = pregnenolone + 4-methylpentanal + 2 oxidized adrenodoxin + 2 H2O |
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Other name(s): | cholesterol desmolase; cytochrome P-450scc; C27-side chain cleavage enzyme; cholesterol 20-22-desmolase; cholesterol C20-22 desmolase; cholesterol side-chain cleavage enzyme; cholesterol side-chain-cleaving enzyme; steroid 20-22 desmolase; steroid 20-22-lyase; CYP11A1 (gene name) | ||||||||||||||||||
Systematic name: | cholesterol,reduced-adrenodoxin:oxygen oxidoreductase (side-chain-cleaving) | ||||||||||||||||||
Comments: | A heme-thiolate protein (cytochrome P-450). The reaction proceeds in three stages, with two hydroxylations at C-22 and C-20 preceding scission of the side-chain between carbons 20 and 22. The initial source of the electrons is NADPH, which transfers the electrons to the adrenodoxin via EC 1.18.1.6, adrenodoxin-NADP+ reductase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37292-81-2, 440354-98-3 | ||||||||||||||||||
References: |
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EC | 1.14.15.12 | ||||||||||||||||||
Transferred entry: | pimeloyl-[acyl-carrier protein] synthase. Now EC 1.14.14.46, pimeloyl-[acyl-carrier protein] synthase | ||||||||||||||||||
EC | 1.14.15.15 | ||||||||||||||||||
Accepted name: | cholestanetriol 26-monooxygenase | ||||||||||||||||||
Reaction: | 5β-cholestane-3α,7α,12α-triol + 6 reduced adrenodoxin + 6 H+ + 3 O2 = (25R)-3α,7α,12α-trihydroxy-5β-cholestan-26-oate + 6 oxidized adrenodoxin + 4 H2O (overall reaction) (1a) 5β-cholestane-3α,7α,12α-triol + 2 reduced adrenodoxin + 2 H+ + O2 = (25R)-5β-cholestane-3α,7α,12α,26-tetraol + 2 oxidized adrenodoxin + H2O (1b) (25R)-5β-cholestane-3α,7α,12α,26-tetraol + 2 reduced adrenodoxin + 2 H+ + O2 = (25R)-3α,7α,12α-trihydroxy-5β-cholestan-26-al + 2 oxidized adrenodoxin + 2 H2O (1c) (25R)-3α,7α,12α-trihydroxy-5β-cholestan-26-al + 2 reduced adrenodoxin + 2 H+ + O2 = (25R)-3α,7α,12α-trihydroxy-5β-cholestan-26-oate + 2 oxidized adrenodoxin + H2O |
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For diagram of cholic acid biosynthesis (sidechain), click here | |||||||||||||||||||
Other name(s): | 5β-cholestane-3α,7α,12α-triol 26-hydroxylase; 5β-cholestane-3α,7α,12α-triol hydroxylase; cholestanetriol 26-hydroxylase; sterol 27-hydroxylase; sterol 26-hydroxylase; cholesterol 27-hydroxylase; CYP27A; CYP27A1; cytochrome P450 27A1′ | ||||||||||||||||||
Systematic name: | 5β-cholestane-3α,7α,12α-triol,adrenodoxin:oxygen oxidoreductase (26-hydroxylating) | ||||||||||||||||||
Comments: | This mitochondrial cytochrome P-450 enzyme requires adrenodoxin. It catalyses the first three sterol side chain oxidations in bile acid biosynthesis via the neutral (classic) pathway. Can also act on cholesterol, cholest-5-ene-3β,7α-diol, 7α-hydroxycholest-4-en-3-one, and 5β-cholestane-3α,7α-diol. The enzyme can also hydroxylate cholesterol at positions 24 and 25. The initial source of the electrons is NADPH, which transfers the electrons to the adrenodoxin via EC 1.18.1.6, adrenodoxin-NADP+ reductase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 52227-77-7 | ||||||||||||||||||
References: |
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EC | 1.14.15.28 | ||||||||||||||||||
Accepted name: | cholest-4-en-3-one 26-monooxygenase [(25R)-3-oxocholest-4-en-26-oate forming] | ||||||||||||||||||
Reaction: | cholest-4-en-3-one + 6 reduced [2Fe-2S] ferredoxin + 3 O2 = (25R)-3-oxocholest-4-en-26-oate + 6 oxidized [2Fe-2S] ferredoxin + 4 H2O (overall reaction) (1a) cholest-4-en-3-one + 2 reduced [2Fe-2S] ferredoxin + O2 = (25R)-26-hydroxycholest-4-en-3-one + 2 oxidized [2Fe-2S] ferredoxin + H2O (1b) (25R)-26-hydroxycholest-4-en-3-one + 2 reduced [2Fe-2S] ferredoxin + O2 = (25R)-26-oxocholest-4-en-3-one + 2 oxidized [2Fe-2S] ferredoxin + 2 H2O (1c) (25R)-26-oxocholest-4-en-3-one + 2 reduced [2Fe-2S] ferredoxin + O2 = (25R)-3-oxocholest-4-en-26-oate + 2 oxidized [2Fe-2S] ferredoxin + H2O |
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Other name(s): | CYP142 | ||||||||||||||||||
Systematic name: | cholest-4-en-3-one,reduced [2Fe-2S] ferredoxin:oxygen oxidoreductase [(25R)-3-oxocholest-4-en-26-oate-forming] | ||||||||||||||||||
Comments: | This cytochrome P-450 (heme-thiolate) enzyme, found in several bacterial pathogens, is involved in degradation of the host cholesterol. It catalyses the hydroxylation of the C-26 carbon, followed by oxidation of the alcohol to the carboxylic acid via the aldehyde intermediate, initiating the degradation of the alkyl side-chain of cholesterol. The products are exclusively in the (25R) conformation. The enzyme also accepts cholesterol as a substrate. cf. EC 1.14.15.29, cholest-4-en-3-one 26-monooxygenase [(25S)-3-oxocholest-4-en-26-oate forming]. The enzyme can receive electrons from ferredoxin reductase in vitro, its natural electron donor is not known yet. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.15.29 | ||||||||||||||||||
Accepted name: | cholest-4-en-3-one 26-monooxygenase [(25S)-3-oxocholest-4-en-26-oate forming] | ||||||||||||||||||
Reaction: | cholest-4-en-3-one + 6 reduced ferredoxin [iron-sulfur] cluster + 6 H+ + 3 O2 = (25S)-3-oxocholest-4-en-26-oate + 6 oxidized ferredoxin [iron-sulfur] cluster + 4 H2O (overall reaction) (1a) cholest-4-en-3-one + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = (25S)-26-hydroxycholest-4-en-3-one + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O (1b) (25S)-26-hydroxycholest-4-en-3-one + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = (25S)-26-oxocholest-4-en-3-one + 2 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O (1c) (25S)-26-oxocholest-4-en-3-one + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = (25S)-3-oxocholest-4-en-26-oate + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O |
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Other name(s): | CYP125; CYP125A1; cholest-4-en-3-one 27-monooxygenase (misleading); cholest-4-en-3-one,NADH:oxygen oxidoreductase (26-hydroxylating); cholest-4-en-3-one 26-monooxygenase (ambiguous) | ||||||||||||||||||
Systematic name: | cholest-4-en-3-one,[reduced ferredoxin]:oxygen oxidoreductase [(25S)-3-oxocholest-4-en-26-oate-forming] | ||||||||||||||||||
Comments: | A cytochrome P-450 (heme-thiolate) protein found in several bacterial pathogens. The enzyme is involved in degradation of the host's cholesterol. It catalyses the hydroxylation of the C-26 carbon, followed by oxidation of the alcohol to the carboxylic acid via the aldehyde intermediate, initiating the degradation of the alkyl side-chain of cholesterol [4]. The products are exclusively in the (25S) configuration. The enzyme is part of a two-component system that also includes a ferredoxin reductase (most likely KshB, which also interacts with EC 1.14.15.30, 3-ketosteroid 9α-monooxygenase). The enzyme also accepts cholesterol as a substrate. cf. EC 1.14.15.28, cholest-4-en-3-one 27-monooxygenase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.15.30 | ||||||||||||||||||
Accepted name: | 3-ketosteroid 9α-monooxygenase | ||||||||||||||||||
Reaction: | androsta-1,4-diene-3,17-dione + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = 9α-hydroxyandrosta-1,4-diene-3,17-dione + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O | ||||||||||||||||||
Other name(s): | KshA; 3-ketosteroid 9α-hydroxylase | ||||||||||||||||||
Systematic name: | androsta-1,4-diene-3,17-dione,[reduced ferredoxin]:oxygen oxidoreductase (9α-hydroxylating) | ||||||||||||||||||
Comments: | The enzyme is involved in the cholesterol degradation pathway of several bacterial pathogens, such as Mycobacterium tuberculosis. It forms a two-component system with a ferredoxin reductase (KshB). The enzyme contains a Rieske-type iron-sulfur center and non-heme iron. The product of the enzyme is unstable, and spontaneously converts to 3-hydroxy-9,10-seconandrost-1,3,5(10)-triene-9,17-dione. | ||||||||||||||||||
Links to other databases: | BRENDA, EAWAG-BBD, EXPASY, KEGG, MetaCyc, PDB | ||||||||||||||||||
References: |
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EC | 1.14.18.8 | ||||||||||||||||||
Transferred entry: | 7α-hydroxycholest-4-en-3-one 12α-hydroxylase. Now included with EC 1.14.14.139, 5β-cholestane-3α,7α-diol 12α-hydroxylase | ||||||||||||||||||
EC | 1.14.18.9 | ||||||||||||||||||
Accepted name: | 4α-methylsterol monooxygenase | ||||||||||||||||||
Reaction: | 4,4-dimethyl-5α-cholest-7-en-3β-ol + 6 ferrocytochrome b5 + 3 O2 + 6 H+ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + 6 ferricytochrome b5 + 4 H2O (overall reaction) (1a) 4,4-dimethyl-5α-cholest-7-en-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4α-hydroxymethyl-4β-methyl-5α-cholest-7-en-3β-ol + 2 ferricytochrome b5 + H2O (1b) 4α-hydroxymethyl-4β-methyl-5α-cholest-7-en-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + 2 ferricytochrome b5 + 2 H2O (1c) 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carbaldehyde + 2 ferrocytochrome b5 + O2 + 2 H+ = 3β-hydroxy-4β-methyl-5α-cholest-7-ene-4α-carboxylate + 2 ferricytochrome b5 + H2O |
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For diagram of sterol ring A modification, click here | |||||||||||||||||||
Other name(s): | methylsterol hydroxylase (ambiguous); 4-methylsterol oxidase (ambiguous); 4,4-dimethyl-5α-cholest-7-en-3β-ol,hydrogen-donor:oxygen oxidoreductase (hydroxylating) (ambiguous); methylsterol monooxygenase (ambiguous); ERG25 (gene name); MSMO1 (gene name); 4,4-dimethyl-5α-cholest-7-en-3β-ol,ferrocytochrome-b5:oxygen oxidoreductase (hydroxylating) (ambiguous) | ||||||||||||||||||
Systematic name: | 4,4-dimethyl-5α-cholest-7-en-3β-ol,ferrocytochrome-b5:oxygen oxidoreductase (C4α-methyl-hydroxylating) | ||||||||||||||||||
Comments: | This enzyme is found in fungi and animals and catalyses a step in the biosynthesis of important sterol molecules such as ergosterol and cholesterol, respectively. The enzyme acts on the 4α-methyl group. Subsequent decarboxylation by EC 1.1.1.170, 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating), occurs concomitantly with epimerization of the remaining 4β-methyl into the 4α position, thus making it a suitable substrate for a second round of catalysis. cf. EC 1.14.13.246, 4β-methylsterol monooxygenase; EC 1.14.18.10, plant 4,4-dimethylsterol C-4α-methyl-monooxygenase; and EC 1.14.18.11, plant 4α-monomethylsterol monooxygenase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37256-80-7 | ||||||||||||||||||
References: |
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EC | 1.14.19.20 | ||||||||||||||||||
Accepted name: | Δ7-sterol 5(6)-desaturase | ||||||||||||||||||
Reaction: | a Δ7-sterol + 2 ferrocytochrome b5 + O2 + 2 H+ = a Δ5,7-sterol + 2 ferricytochrome b5 + 2 H2O | ||||||||||||||||||
For diagram of the modification of sterol rings B, C and D, click here | |||||||||||||||||||
Other name(s): | lathosterol oxidase; Δ7-sterol Δ5-dehydrogenase; Δ7-sterol 5-desaturase; Δ7-sterol-C5(6)-desaturase; 5-DES; SC5DL (gene name); ERG3 (gene name) | ||||||||||||||||||
Systematic name: | Δ7-sterol,ferrocytochrome b5:oxygen oxidoreductase 5,6-dehydrogenating | ||||||||||||||||||
Comments: | This enzyme, found in eukaryotic organisms, catalyses the introduction of a double bond between the C5 and C6 carbons of the B ring of Δ7-sterols, to yield the corresponding Δ5,7-sterols. The enzymes from yeast, plants and vertebrates act on avenasterol, episterol, and lathosterol, respectively. The enzyme is located at the endoplasmic reticulum and is membrane bound. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37255-37-1 | ||||||||||||||||||
References: |
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EC | 1.14.19.21 | ||||||||||||||||||
Accepted name: | cholesterol 7-desaturase | ||||||||||||||||||
Reaction: | cholesterol + O2 + NAD(P)H + H+ = cholesta-5,7-dien-3β-ol + NAD(P)+ + 2 H2O | ||||||||||||||||||
Other name(s): | nvd (gene name); daf-36 (gene name) | ||||||||||||||||||
Systematic name: | cholesterol,NAD(P)H:oxygen oxidoreductase (7,8 dehydrogenating) | ||||||||||||||||||
Comments: | The enzyme, characterized from several organisms including the worm Caenorhabditis elegans, the fly Drosophila melanogaster, and the ciliate Tetrahymena thermophila, is a Rieske oxygenase. In insects it participates in the the biosythesis of ecdysteroid hormones. The electrons are transferred from NAD(P)H via an electron transfer chain likely to include ferredoxin reductase and ferredoxin. The enzyme differs from regular desaturases, such as EC 1.14.19.20, 7-sterol 5(6)-desaturase, which are cytochrome b5-dependent and contain the three His-boxes that are typical to most desaturases. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc | ||||||||||||||||||
References: |
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EC | 1.14.21.6 | ||||||||||||||||||
Transferred entry: | lathosterol oxidase. Now EC 1.14.19.20, Δ7-sterol 5(6)-desaturase | ||||||||||||||||||
EC | 1.14.99.7 | ||||||||||||||||||
Transferred entry: | squalene monooxygenase. Transferred to EC 1.14.13.132, squalene monooxygenase. | ||||||||||||||||||
EC | 1.14.99.38 | ||||||||||||||||||
Accepted name: | cholesterol 25-monooxygenase | ||||||||||||||||||
Reaction: | cholesterol + reduced acceptor + O2 = 25-hydroxycholesterol + acceptor + H2O | ||||||||||||||||||
For diagram of cholic acid biosynthesis (sidechain), click here | |||||||||||||||||||
Glossary: | cholesterol = cholest-5-en-3β-ol | ||||||||||||||||||
Other name(s): | cholesterol 25-hydroxylase (ambiguous) | ||||||||||||||||||
Systematic name: | cholesterol,hydrogen-donor:oxygen oxidoreductase (25-hydroxylating) | ||||||||||||||||||
Comments: | Unlike most other sterol hydroxylases, this enzyme is not a cytochrome P-450. Instead, it uses diiron cofactors to catalyse the hydroxylation of hydrophobic substrates [1]. The diiron cofactor can be either Fe-O-Fe or Fe-OH-Fe and is bound to the enzyme through interactions with clustered histidine or glutamate residues [4,5]. In cell cultures, this enzyme down-regulates cholesterol synthesis and the processing of sterol regulatory element binding proteins (SREBPs). cf. EC 1.17.99.10, cholesterol C-25 hydroxylase. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 60202-07-5 | ||||||||||||||||||
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EC | 1.17.99.10 | ||||||||||||||||||
Accepted name: | steroid C-25 hydroxylase | ||||||||||||||||||
Reaction: | cholest-4-en-3-one + acceptor + H2O = 25-hydroxycholest-4-en-3-one + reduced acceptor | ||||||||||||||||||
Other name(s): | s25dA1 (gene name); s25dA1B3 (gene name); s25dA1C3 (gene name); cholesterol C-25 dehydrogenase; steroid C-25 dehydrogenase | ||||||||||||||||||
Systematic name: | cholest-4-en-3-one:acceptor oxidoreductase (25-hydroxylating) | ||||||||||||||||||
Comments: | The enzyme, characterized from the bacterium Sterolibacterium denitrificans, participates in the anaerobic degradation of cholesterol. The enzyme can accept several substrates including vitamin D3. The enzyme contains a bis(guanylyl molybdopterin) cofactor, five [Fe-S] clusters, and one heme b. cf. EC 1.14.99.38, cholesterol 25-monooxygenase, an oxygen-requiring eukaryotic enzyme that catalyses a similar transformation. | ||||||||||||||||||
Links to other databases: | BRENDA, EXPASY, KEGG, MetaCyc | ||||||||||||||||||
References: |
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