The Enzyme Database

Your query returned 4 entries.    printer_iconPrintable version

EC 1.14.18.1     
Accepted name: tyrosinase
Reaction: (1) L-tyrosine + O2 = dopaquinone + H2O (overall reaction)
(1a) L-tyrosine + ½ O2 = L-dopa
(1b) L-dopa + ½ O2 = dopaquinone + H2O
(2) 2 L-dopa + O2 = 2 dopaquinone + 2 H2O
For diagram of melanin biosynthesis, click here
Other name(s): monophenol monooxygenase; phenolase; monophenol oxidase; cresolase; monophenolase; tyrosine-dopa oxidase; monophenol monooxidase; monophenol dihydroxyphenylalanine:oxygen oxidoreductase; N-acetyl-6-hydroxytryptophan oxidase; monophenol, dihydroxy-L-phenylalanine oxygen oxidoreductase; o-diphenol:O2 oxidoreductase; phenol oxidase
Systematic name: L-tyrosine,L-dopa:oxygen oxidoreductase
Comments: A type III copper protein found in a broad variety of bacteria, fungi, plants, insects, crustaceans, and mammals, which is involved in the synthesis of betalains and melanin. The enzyme, which is activated upon binding molecular oxygen, can catalyse both a monophenolase reaction cycle (reaction 1) or a diphenolase reaction cycle (reaction 2). During the monophenolase cycle, one of the bound oxygen atoms is transferred to a monophenol (such as L-tyrosine), generating an o-diphenol intermediate, which is subsequently oxidized to an o-quinone and released, along with a water molecule. The enzyme remains in an inactive deoxy state, and is restored to the active oxy state by the binding of a new oxygen molecule. During the diphenolase cycle the enzyme binds an external diphenol molecule (such as L-dopa) and oxidizes it to an o-quinone that is released along with a water molecule, leaving the enzyme in the intermediate met state. The enzyme then binds a second diphenol molecule and repeats the process, ending in a deoxy state [7]. The second reaction is identical to that catalysed by the related enzyme catechol oxidase (EC 1.10.3.1). However, the latter can not catalyse the hydroxylation or monooxygenation of monophenols.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 9002-10-2
References:
1.  Dawson, C.R. and Tarpley, W.B. The copper oxidases. In: Sumner, J.B. and Myrbäck, K. (Ed.), The Enzymes, 1st edn, vol. 2, Academic Press, New York, 1951, pp. 454–498.
2.  Patil, S.S. and Zucker, M. Potato phenolases. Purification and properties. J. Biol. Chem. 240 (1965) 3938–3943. [PMID: 5842066]
3.  Pomerantz, S.H. Separation, purification, and properties of two tyrosinases from hamster melanoma. J. Biol. Chem. 238 (1963) 2351–2357. [PMID: 13972077]
4.  Robb, D.A. `Tyrosinase. In: Lontie, R. (Ed.), Copper Proteins and Copper Enzymes, vol. 2, CRC Press, Boca Raton, FL, 1984, pp. 207–240.
5.  Sanchez-Ferrer, A., Rodriguez-Lopez, J.N., Garcia-Canovas, F. and Garcia-Carmona, F. Tyrosinase: a comprehensive review of its mechanism. Biochim. Biophys. Acta 1247 (1995) 1–11. [DOI] [PMID: 7873577]
6.  Steiner, U., Schliemann, W. and Strack, D. Assay for tyrosine hydroxylation activity of tyrosinase from betalain-forming plants and cell cultures. Anal. Biochem. 238 (1996) 72–75. [DOI] [PMID: 8660589]
7.  Rolff, M., Schottenheim, J., Decker, H. and Tuczek, F. Copper-O2 reactivity of tyrosinase models towards external monophenolic substrates: molecular mechanism and comparison with the enzyme. Chem Soc Rev 40 (2011) 4077–4098. [DOI] [PMID: 21416076]
[EC 1.14.18.1 created 1972, modified 1976, modified 1980 (EC 1.14.17.2 created 1972, incorporated 1984), modified 2012]
 
 
EC 1.14.18.10     
Accepted name: plant 4,4-dimethylsterol C-4α-methyl-monooxygenase
Reaction: 24-methylidenecycloartanol + 6 ferrocytochrome b5 + 3 O2 + 6 H+ = 3β-hydroxy-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-4α-carboxylate + 6 ferricytochrome b5 + 4 H2O (overall reaction)
(1a) 24-methylidenecycloartanol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4α-(hydroxymethyl)-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-3β-ol + 2 ferricytochrome b5 + H2O
(1b) 4α-(hydroxymethyl)-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4α-formyl-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-3β-ol + 2 ferricytochrome b5 + 2 H2O
(1c) 4α-formyl-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 3β-hydroxy-4β,14α-dimethyl-9β,19-cyclo-5α-ergost-24(241)-en-4α-carboxylate + 2 ferricytochrome b5 + H2O
Glossary: 24-methylidenecycloartanol = 4α,4β,14α-trimethyl-9β,19-cyclo-5α-ergost-24(241)-en-3β-ol
Other name(s): SMO1 (gene name)
Systematic name: 24-methylidenecycloartanol,ferrocytochrome-b5:oxygen oxidoreductase (C-4α-methyl-hydroxylating)
Comments: This plant enzyme catalyses a step in the biosynthesis of sterols. It acts on the 4α-methyl group of the 4,4-dimethylated intermediate 24-methylidenecycloartanol and catalyses three successive oxidations, turning it into a carboxyl group. The carboxylate is subsequently removed by EC 1.1.1.418, plant 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating), which also catalyses the epimerization of the remaining 4β-methyl into the 4α position. Unlike the fungal/animal enzyme EC 1.14.18.9, 4α-methylsterol monooxygenase, this enzyme is not able to remove the methyl group from C-4-monomethylated substrates. That activity is performed in plants by a second enzyme, EC 1.14.18.11, plant 4α-monomethylsterol monooxygenase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Pascal, S., Taton, M. and Rahier, A. Plant sterol biosynthesis. Identification and characterization of two distinct microsomal oxidative enzymatic systems involved in sterol C4-demethylation. J. Biol. Chem. 268 (1993) 11639–11654. [PMID: 8505296]
2.  Rahier, A., Smith, M. and Taton, M. The role of cytochrome b5 in 4α-methyl-oxidation and C5(6) desaturation of plant sterol precursors. Biochem. Biophys. Res. Commun. 236 (1997) 434–437. [DOI] [PMID: 9240456]
3.  Darnet, S., Bard, M. and Rahier, A. Functional identification of sterol-4α-methyl oxidase cDNAs from Arabidopsis thaliana by complementation of a yeast erg25 mutant lacking sterol-4α-methyl oxidation. FEBS Lett. 508 (2001) 39–43. [PMID: 11707264]
4.  Darnet, S. and Rahier, A. Plant sterol biosynthesis: identification of two distinct families of sterol 4α-methyl oxidases. Biochem. J. 378 (2004) 889–898. [PMID: 14653780]
[EC 1.14.18.10 created 2019]
 
 
EC 1.14.18.11     
Accepted name: plant 4α-monomethylsterol monooxygenase
Reaction: 24-methylidenelophenol + 6 ferrocytochrome b5 + 3 O2 + 6 H+ = 3β-hydroxyergosta-7,24(241)-dien-4α-carboxylate + 6 ferricytochrome b5 + 4 H2O (overall reaction)
(1a) 24-methylidenelophenol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4α-(hydroxymethyl)ergosta-7,24(241)-dien-3β-ol + 2 ferricytochrome b5 + H2O
(1b) 4α-(hydroxymethyl)ergosta-7,24(241)-dien-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 4α-formylergosta-7,24(241)-dien-3β-ol + 2 ferricytochrome b5 + 2 H2O
(1c) 4α-formylergosta-7,24(241)-dien-3β-ol + 2 ferrocytochrome b5 + O2 + 2 H+ = 3β-hydroxyergosta-7,24(241)-dien-4α-carboxylate + 2 ferricytochrome b5 + H2O
Glossary: 24-methylidenelophenol = 4α-methyl-5α-ergosta-7,24-dien-3β-ol
Other name(s): SMO2 (gene name)
Systematic name: 24-ethylidenelophenol,ferrocytochrome-b5:oxygen oxidoreductase (C-4α-methyl-hydroxylating)
Comments: This plant enzyme catalyses a step in the biosynthesis of sterols. It acts on the methyl group of the 4α-methylated intermediates 24-ethylidenelophenol and 24-methylidenelophenol and catalyses three successive oxidations, turning it into a carboxyl group. The carboxylate is subsequently removed by EC 1.1.1.418, plant 3β-hydroxysteroid-4α-carboxylate 3-dehydrogenase (decarboxylating). Unlike the fungal/animal enzyme EC 1.14.18.9, 4α-methylsterol monooxygenase, this enzyme is not able to act on 4,4-dimethylated substrates. That activity, which occurs earlier in the pathway, is performed in plants by a second enzyme, EC 1.14.18.10, plant 4,4-dimethylsterol C-4α-methyl-monooxygenase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Pascal, S., Taton, M. and Rahier, A. Plant sterol biosynthesis. Identification and characterization of two distinct microsomal oxidative enzymatic systems involved in sterol C4-demethylation. J. Biol. Chem. 268 (1993) 11639–11654. [PMID: 8505296]
2.  Rahier, A., Smith, M. and Taton, M. The role of cytochrome b5 in 4α-methyl-oxidation and C5(6) desaturation of plant sterol precursors. Biochem. Biophys. Res. Commun. 236 (1997) 434–437. [DOI] [PMID: 9240456]
3.  Darnet, S., Bard, M. and Rahier, A. Functional identification of sterol-4α-methyl oxidase cDNAs from Arabidopsis thaliana by complementation of a yeast erg25 mutant lacking sterol-4α-methyl oxidation. FEBS Lett. 508 (2001) 39–43. [PMID: 11707264]
4.  Darnet, S. and Rahier, A. Plant sterol biosynthesis: identification of two distinct families of sterol 4α-methyl oxidases. Biochem. J. 378 (2004) 889–898. [PMID: 14653780]
[EC 1.14.18.11 created 2019]
 
 
EC 1.14.18.12     
Accepted name: 2-hydroxy fatty acid dioxygenase
Reaction: a (2R)-2-hydroxy Cn-fatty acid + O2 = a Cn-1-fatty acid + H2O + CO2
Other name(s): MPO1 (gene name)
Systematic name: 2-hydroxyfatty acid:oxygen oxidoreductase (CO2,H2O-forming)
Comments: Requires iron(II). The enzyme, characterized from yeast, is involved in phytosphingosine metabolism. The reaction is mediated by iron(IV) peroxide and results in the release of a water molecule and a carbon dioxide molecule, shortening the substrate by a single carbon atom and forming an odd-numbered fatty acid. Both oxygen atoms of the original carboxylate group are released - one as the leaving water molecule, the other as one of the oxygens of the carbon dioxide molecule. The two oxygen atoms in the newly-formed carboxylate originate from the 2-hydroxy group and from molecular oxygen, respectively. The other oxygen atom of the molecular oxygen is incorporated into the leaving CO2 molecule. The enzyme from the yeast Saccharomyces cerevisiae is active at least toward C14 to C26 2-hydroxyfatty acids, but not against C8 2-hydroxyfatty acid.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Kondo, N., Ohno, Y., Yamagata, M., Obara, T., Seki, N., Kitamura, T., Naganuma, T. and Kihara, A. Identification of the phytosphingosine metabolic pathway leading to odd-numbered fatty acids. Nat. Commun. 5:5338 (2014). [PMID: 25345524]
2.  Seki, N., Mori, K., Kitamura, T., Miyamoto, M. and Kihara, A. Yeast Mpo1 is a novel dioxygenase that catalyzes the α-oxidation of a 2-hydroxy fatty acid in an Fe2+-dependent manner. Mol. Cell Biol. 39:e00428-18 (2019). [DOI] [PMID: 30530523]
[EC 1.14.18.12 created 2020]
 
 


Data © 2001–2024 IUBMB
Web site © 2005–2024 Andrew McDonald