7-methylxanthosine synthase

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:xanthosine N7-methyltransferase. Other names in common use include xanthosine methyltransferase, XMT, xanthosine:S-adenosyl-L-methionine methyltransferase, CtCS1, CmXRS1, CaXMT1, and S-adenosyl-L-methionine:xanthosine 7-N-methyltransferase.

References

Negishi O, Ozawa T and Imagawa H (1985). "The role of xanthosine in the biosynthesis of caffeine in coffee plants". Agric. Biol. Chem. 49: 2221–2222. doi:10.1271/bbb1961.49.2221.
Mizuno K, Kato M, Irino F, Yoneyama N, Fujimura T, Ashihara H (2003). "The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.)". FEBS Lett. 547 (1-3): 56–60. doi:10.1016/S0014-5793(03)00670-7. PMID 12860386.
Uefuji H, Ogita S, Yamaguchi Y, Koizumi N, Sano H (2003). "Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants". Plant. Physiol. 132 (1): 372–80. doi:10.1104/pp.102.019679. PMC 166982. PMID 12746542.
Yoneyama N, Morimoto H, Ye CX, Ashihara H, Mizuno K, Kato M (2006). "Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme". Mol. Genet. Genomics. 275 (2): 125–35. doi:10.1007/s00438-005-0070-z. PMID 16333668.

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

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

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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