sterol 24-C-methyltransferase

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In enzymology, a sterol 24-C-methyltransferase (EC 2.1.1.41) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + 5alpha-cholesta-8,24-dien-3beta-ol

\rightleftharpoons

S-adenosyl-L-homocysteine + 24-methylene-5alpha-cholest-8-en-3beta-ol

Thus, the two substrates of this enzyme are S-adenosyl methionine and 5alpha-cholesta-8,24-dien-3beta-ol, whereas its two products are S-adenosylhomocysteine and 24-methylene-5alpha-cholest-8-en-3beta-ol.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:zymosterol 24-C-methyltransferase. Other names in common use include Delta24-methyltransferase, Delta24-sterol methyltransferase, zymosterol-24-methyltransferase, S-adenosyl-4-methionine:sterol Delta24-methyltransferase, SMT1, 24-sterol C-methyltransferase, S-adenosyl-L-methionine:Delta24(23)-sterol methyltransferase, and phytosterol methyltransferase. This enzyme participates in biosynthesis of steroids. It employs one cofactor, glutathione.

References

Moore JT, Gaylor JL (1969). "Isolation and purification of an S-adenosylmethionine: delta 24-sterol methyltransferase from yeast". J. Biol. Chem. 244 (23): 6334–40. PMID 5354959.
Venkatramesh M, Guo DA, Jia Z, Nes WD (1996). "Mechanism and structural requirements for transformation of substrates by the (S)-adenosyl-L-methionine:delta 24(25)-sterol methyl transferase from Saccharomyces cerevisiae". Biochim. Biophys. Acta. 1299 (3): 313–24. doi:10.1016/0005-2760(95)00218-9. PMID 8597586.
MD, Zhou W, Lopez M, Nes WD (1997). ", Stereochemical features of C-methylation on the path to Delta24(28)-methylene and Delta24(28)-ethylidene sterols: studies on the recombinant phytosterol methyl transferase from Arabidopsis thaliana". Tetrahedron Lett. 38 (35): 6115–6118. doi:10.1016/S0040-4039(97)01386-5.
Bouvier-Nave P, Husselstein T, Benveniste P (1998). "Two families of sterol methyltransferases are involved in the first and the second methylation steps of plant sterol biosynthesis". Eur. J. Biochem. 256 (1): 88–96. doi:10.1046/j.1432-1327.1998.2560088.x. PMID 9746350.
Nes WD, McCourt BS, Zhou WX, Ma J, Marshall JA, Peek LA, Brennan M (1998). "Overexpression, purification, and stereochemical studies of the recombinant (S)-adenosyl-L-methionine: delta 24(25)- to delta 24(28)-sterol methyl transferase enzyme from Saccharomyces cerevisiae". Arch. Biochem. Biophys. 353 (2): 297–311. doi:10.1006/abbi.1998.0665. PMID 9606964.

Transferase: one carbon transferases (EC 2.1)

2.1.1: Methyl-

N-	Histamine N-methyltransferase Phenylethanolamine N-methyltransferase Amine N-methyltransferase Phosphatidylethanolamine N-methyltransferase
O-	5-hydroxyindole-O-methyltransferase/Acetylserotonin O-methyltransferase Catechol-O-methyl transferase
Homocysteine	Betaine-homocysteine methyltransferase Homocysteine methyltransferase Methionine synthase
Other	Phosphatidyl ethanolamine methyltransferase DNMT3B Histone methyltransferase Thymidylate synthase DNA methyltransferase Thiopurine methyltransferase Cyclopropane-fatty-acyl-phospholipid synthase

2.1.2: Hydroxymethyl-,
Formyl- and Related

Hydroxymethyltransferase	Serine hydroxymethyltransferase 3-methyl-2-oxobutanoate hydroxymethyltransferase
Formyltransferase	Phosphoribosylglycinamide formyltransferase Inosine monophosphate synthase
Other	Glutamate formimidoyltransferase Aminomethyltransferase

2.1.3: Carboxy-
and Carbamoyl

Carboxy	methylmalonyl-CoA carboxytransferase
Carbamoyl	Aspartate carbamoyltransferase Ornithine carbamoyltransferase Oxamate carbamoyltransferase Putrescine carbamoyltransferase 3-hydroxymethylcephem carbamoyltransferase Lysine carbamoyltransferase N-acetylornithine carbamoyltransferase

2.1.4: Amidine

Arginine:glycine amidinotransferase

v t e Enzymes
Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Diffusion-limited enzyme Cofactor Enzyme catalysis
Regulation	Allosteric regulation Cooperativity Enzyme inhibitor Enzyme activator
Classification	EC number Enzyme superfamily Enzyme family List of enzymes
Kinetics	Enzyme kinetics Eadie–Hofstee diagram Hanes–Woolf plot Lineweaver–Burk plot Michaelis–Menten kinetics
Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list) EC7 Translocases (list)