Squalene methyltransferase

Squalene methyltransferase (EC 2.1.1.262, TMT-1, TMT-2) is an enzyme with systematic name S-adenosyl-L-methionine:squalene C-methyltransferase.^[1] This enzyme catalyses the following chemical reaction

\rightleftharpoons

2 S-adenosyl-L-homocysteine + 3,22-dimethyl-1,2,23,24-tetradehydro-2,3,22,23-tetrahydrosqualene (overall reaction)

(1a) S-adenosyl-L-methionine + squalene

\rightleftharpoons

S-adenosyl-L-homocysteine + 3-methyl-1,2-didehydro-2,3-dihydrosqualene

(1b) S-adenosyl-L-methionine + 3-methyl-1,2-didehydro-2,3-dihydrosqualene

\rightleftharpoons

S-adenosyl-L-homocysteine + 3,22-dimethyl-1,2,23,24-tetradehydro-2,3,22,23-tetrahydrosqualene

There are two isoforms in the green alga Botryococcus braunii BOT22 that differ in their specificity .

References

↑ Niehaus, T.D.; Kinison, S.; Okada, S.; Yeo, Y.S.; Bell, S.A.; Cui, P.; Devarenne, T.P.; Chappell, J. (2012). "Functional identification of triterpene methyltransferases from Botryococcus braunii race B". J. Biol. Chem. 287: 8163–8173. doi:10.1074/jbc.m111.316059. PMID 22241476.

Transferase: one carbon transferases (EC 2.1)

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

Hydroxymethyltransferase	Serine hydroxymethyltransferase 3-methyl-2-oxobutanoate hydroxymethyltransferase

Formyltransferase	Phosphoribosylglycinamide formyltransferase Inosine monophosphate synthase

Other	Glutamate formimidoyltransferase Aminomethyltransferase

Carboxy	methylmalonyl-CoA carboxytransferase

Carbamoyl	Aspartate carbamoyltransferase Ornithine carbamoyltransferase Oxamate carbamoyltransferase Putrescine carbamoyltransferase 3-hydroxymethylcephem carbamoyltransferase Lysine carbamoyltransferase N-acetylornithine carbamoyltransferase

Enzymes

Activity	Active site Binding site Catalytic triad Oxyanion hole Enzyme promiscuity Catalytically perfect enzyme Coenzyme Cofactor Enzyme catalysis Enzyme kinetics Lineweaver–Burk plot Michaelis–Menten kinetics

Regulation	Allosteric regulation Cooperativity Enzyme inhibitor

Classification	EC number Enzyme superfamily Enzyme family List of enzymes

Types	EC1 Oxidoreductases (list) EC2 Transferases (list) EC3 Hydrolases (list) EC4 Lyases (list) EC5 Isomerases (list) EC6 Ligases (list)

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