The Enzyme Database

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Accepted name: sterol 24-C-methyltransferase
Reaction: S-adenosyl-L-methionine + 5α-cholesta-8,24-dien-3β-ol = S-adenosyl-L-homocysteine + 24-methylene-5α-cholest-8-en-3β-ol
For diagram of sterol sidechain modification, click here
Glossary: desmosterol = cholesta-5,24-dien-3β-ol
zymostrol = 5α-cholesta-8,24-dien-3β-ol
Other name(s): Δ24-methyltransferase; Δ24-sterol methyltransferase; zymosterol-24-methyltransferase; S-adenosyl-4-methionine:sterol Δ24-methyltransferase; SMT1; 24-sterol C-methyltransferase; S-adenosyl-L-methionine:Δ24(23)-sterol methyltransferase; phytosterol methyltransferase
Systematic name: S-adenosyl-L-methionine:zymosterol 24-C-methyltransferase
Comments: Requires glutathione. Acts on a range of sterols with a 24(25)-double bond in the sidechain. While zymosterol is the preferred substrate it also acts on desmosterol, 5α-cholesta-7,24-dien-3β-ol, 5α-cholesta-5,7,24-trien-3β-ol, 4α-methylzymosterol and others. S-Adenosyl-L-methionine attacks the Si-face of the 24(25) double bond and the C-24 hydrogen is transferred to C-25 on the Re face of the double bond.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 37257-07-1
1.  Moore, J.T., Jr. and Gaylor, J.L. Isolation and purification of an S-adenosylmethionine: Δ24-sterol methyltransferase from yeast. J. Biol. Chem. 244 (1969) 6334–6340. [PMID: 5354959]
2.  Venkatramesh, M., Guo, D., Jia, Z. and Nes, W.D. Mechanism and structural requirements for transformations of substrates by the S-adenosyl-L-methionine:Δ24(25)-sterol methyl transferase enzyme from Saccharomyces cerevisiae. Biochim. Biophys. Acta 1299 (1996) 313–324. [DOI] [PMID: 8597586]
3.  Tong, Y., McCourt, B.S., Guo, D., Mangla, A.T., Zhou, W.X., Jenkins, M.D., Zhou, W., Lopez, M. and Nes, W.D. , Stereochemical features of C-methylation on the path to Δ24(28)-methylene and Δ24(28)-ethylidene sterols: studies on the recombinant phytosterol methyl transferase from Arabidopsis thaliana. Tetrahedron Lett. 38 (1997) 6115–6118.
4.  Bouvier-Navé, P., Husselstein, T. and Benveniste, P. Two families of sterol methyltransferases are involved in the first and the second methylation steps of plant biosynthesis. Eur. J. Biochem. 256 (1998) 88–96. [DOI] [PMID: 9746350]
5.  Nes, W.D., McCourt, B.S., Zhou, W., Ma, J., Marshall, J.A., Peek, L.A. and Brennan, M. Overexpression, purification, and stereochemical studies of the recombinant S-adenosyl-L-methionine:Δ24(25)- to Δ24(28)-sterol methyl transferase enzyme from Saccharomyces cerevisiae sterol methyl transferase. Arch. Biochem. Biophys. 353 (1998) 297–311. [DOI] [PMID: 9606964]
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