7-methylxanthosine synthase

In enzymology, a 7-methylxanthosine synthase (EC 2.1.1.158) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + xanthosine S-adenosyl-L-homocysteine + 7-methylxanthosine

Thus, the two substrates of this enzyme are S-adenosyl methionine and xanthosine, whereas its two products are S-adenosylhomocysteine and 7-methylxanthosine.

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 & Imagawa H (1985). "The role of xanthosine in the biosynthesis of caffeine in coffee plants". Agric. Biol. Chem. 49: 2221&ndash, 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&ndash, 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&ndash, 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&ndash, 35. doi:10.1007/s00438-005-0070-z. PMID 16333668.