The Enzyme Database

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EC 1.14.13.70      
Transferred entry: sterol 14α-demethylase. Now EC 1.14.14.154, sterol 14α-demethylase
[EC 1.14.13.70 created 2001, modified 2013, deleted 2018]
 
 
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
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:
1.  Alexander, K., Akhtar, M., Boar, R.B., McGhie, J.F. and Barton, D.H.R. The removal of the 32-carbon atom as formic acid in cholesterol biosynthesis. J. Chem. Soc. Chem. Commun. (1972) 383–385.
2.  Yoshida, Y. and Aoyama, Y. Yeast cytochrome P-450 catalyzing lanosterol 14 α-demethylation. I. Purification and spectral properties. J. Biol. Chem. 259 (1984) 1655–1660. [PMID: 6363414]
3.  Aoyama, Y., Yoshida, Y. and Sato, R. Yeast cytochrome P-450 catalyzing lanosterol 14 α-demethylation. II. Lanosterol metabolism by purified P-45014DM and by intact microsomes. J. Biol. Chem. 259 (1984) 1661–1666. [PMID: 6420412]
4.  Aoyama, Y. and Yoshida, Y. Different substrate specificities of lanosterol 14α-demethylase (P-45014DM) of Saccharomyces cerevisiae and rat liver of 24-methylene-24,25-dihydrolanosterol and 24,25-dihydrolanosterol. Biochem. Biophys. Res. Commun. 178 (1991) 1064–1071. [DOI] [PMID: 1872829]
5.  Aoyama, Y. and Yoshida, Y. The 4β-methyl group of substrate does not affect the activity of lanosterol 14α-demethylase (P45014DM) of yeast: differences between the substrate recognition by yeast and plant sterol 14α-demethylases. Biochem. Biophys. Res. Commun. 183 (1992) 1266–1272. [DOI] [PMID: 1567403]
6.  Bak, S., Kahn, R.A., Olsen, C.E. and Halkier, B.A. Cloning and expression in Escherichia coli of the obtusifoliol 14α-demethylase of Sorghum bicolor (L.) Moench, a cytochrome P450 orthologous to the sterol 14α-demethylases (CYP51) from fungi and mammals. Plant J. 11 (1997) 191–201. [DOI] [PMID: 9076987]
[EC 1.14.14.154 created 2001 as EC 1.14.13.70, modified 2013, transferred 2018 EC 1.14.14.154]
 
 
EC 5.5.1.9     
Accepted name: cycloeucalenol cycloisomerase
Reaction: cycloeucalenol = obtusifoliol
For diagram of plant sterol biosynthesis, click here
Other name(s): cycloeucalenol—obtusifoliol isomerase; cycloeucalenol lyase (cyclopropane-decyclizing)
Systematic name: cycloeucalenol lyase (cyclopropane-ring opening)
Comments: Opens the cyclopropane ring of a number of related 4α-methyl-9β-19-cyclosterols, but not those with a 4β-methyl group, with formation of an 8(9) double bond. Involved in the synthesis of plant sterols.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 60496-19-7
References:
1.  Heintz, R. and Benveniste, P. Plant sterol metabolism. Enzymatic cleavage of the 9β,19β-cyclopropane ring of cyclopropyl sterols in bramble tissue cultures. J. Biol. Chem. 249 (1974) 4267–4274. [PMID: 4369016]
2.  Rahier, A., Schmitt, P. and Benveniste, P. 7-oxo-24ξ(28)-dihydrocycloeucalenol, a potent inhibitor of plant sterol biosynthesis. Phytochemistry 21 (1982) 1969–1974.
[EC 5.5.1.9 created 1986]
 
 


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