Reaction: ergosta-5,7,24(28)-trien-3β-ol + NADPH + H+ + O2 = ergosta-5,7,22,24(28)-tetraen-3β-ol + NADP+ + 2 H2O
For diagram of reaction click here.
Other name(s): ERG5 (gene name); CYP710A (gene name)
Systematic name: ergosta-5,7,24(28)-trien-3β-ol,NADPH:oxygen oxidoreductase 22,23-dehydrogenating
Comments: A heme-thiolate protein (P450). The enzyme, found in yeast and plants, catalyses the introduction of a double bond between the C-22 and C-23 carbons of certain sterols. In yeast the enzyme acts on ergosta-5,7,24(28)-trien-3β-ol, a step in the biosynthesis of ergosterol. The enzyme from the plant Arabidopsis thaliana acts on sitosterol and 24-epi-campesterol, producing stigmasterol and brassicasterol, respectively.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. Kelly, S.L., Lamb, D.C., Corran, A.J., Baldwin, B.C., Parks, L.W. and Kelly, D.E. Purification and reconstitution of activity of Saccharomyces cerevisiae P450 61, a sterol Δ22-desaturase. FEBS Lett. 377 (1995) 217-220. [PMID: 8543054]
2. Skaggs, B.A., Alexander, J.F., Pierson, C.A., Schweitzer, K.S., Chun, K.T., Koegel, C., Barbuch, R. and Bard, M. Cloning and characterization of the Saccharomyces cerevisiae C-22 sterol desaturase gene, encoding a second cytochrome P-450 involved in ergosterol biosynthesis. Gene 169 (1996) 105-109. [PMID: 8635732]
3. Morikawa, T., Mizutani, M., Aoki, N., Watanabe, B., Saga, H., Saito, S., Oikawa, A., Suzuki, H., Sakurai, N., Shibata, D., Wadano, A., Sakata, K. and Ohta, D. Cytochrome P450 CYP710A encodes the sterol C-22 desaturase in Arabidopsis and tomato. Plant Cell 18 (2006) 1008-1022. [PMID: 16531502]