Protein-S-isoprenylcysteine O-methyltransferase

The isoprenylcysteine o-methyltransferase (EC 2.1.1.100) carries out carboyxl methylation of cleaved eukaryotic proteins that terminate in a CaaX motif. In Saccharomyces cerevisiae (Baker's yeast) this methylation is carried out by Ste14p, an integral endoplasmic reticulum membrane protein. Ste14p is the founding member of the isoprenylcysteine carboxyl methyltransferase (ICMT) family, whose members share significant sequence homology.^[1]

S-adenosyl-L-methionine + protein C-terminal S-farnesyl-L-cysteine

\rightleftharpoons

S-adenosyl-L-homocysteine + protein C-terminal S-farnesyl-L-cysteine methyl ester

Thus, the two substrates of this enzyme are S-adenosyl methionine and protein C-terminal S-farnesyl-L-cysteine, whereas its two products are S-adenosylhomocysteine and protein C-terminal S-farnesyl-L-cysteine methyl ester.

References

Clarke S, Vogel JP, Deschenes RJ, Stock J (1988). "Posttranslational modification of the Ha-ras oncogene protein: evidence for a third class of protein carboxyl methyltransferases". Proc. Natl. Acad. Sci. U.S.A. 85 (13): 4643–7. doi:10.1073/pnas.85.13.4643. PMC 280491. PMID 3290900.
Ota IM, Clarke S (1989). "Enzymatic methylation of 23-29-kDa bovine retinal rod outer segment membrane proteins. Evidence for methyl ester formation at carboxyl-terminal cysteinyl residues". J. Biol. Chem. 264 (22): 12879–84. PMID 2753892.
Stephenson RC, Clarke S (1990). "Identification of a C-terminal protein carboxyl methyltransferase in rat liver membranes utilizing a synthetic farnesyl cysteine-containing peptide substrate". J. Biol. Chem. 265 (27): 16248–54. PMID 2398053.

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)

This article incorporates text from the public domain Pfam and InterPro IPR007269

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