EC - 7-methylxanthosine synthase

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IntEnz Enzyme Nomenclature


Accepted name:
7-methylxanthosine synthase
Other names:
xanthosine methyltransferase
xanthosine:S-adenosyl-L-methionine methyltransferase
S-adenosyl-L-methionine:xanthosine 7-N-methyltransferase
Systematic name:
S-adenosyl-L-methionine:xanthosine N7-methyltransferase



The enzyme is specific for xanthosine, as XMP and xanthine cannot act as substrates [2,4]. The enzyme does not have N1- or N3- methylation activity [2]. This is the first methylation step in the production of caffeine.

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , DIAGRAM , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Structural data: CSA , EC2PDB


  1. Negishi, O., Ozawa, T. and Imagawa, H.
    The role of xanthosine in the biosynthesis of caffeine in coffee plants.
    Agric. Biol. Chem. 49: 2221-2222 (1985).
  2. Mizuno, K., Kato, M., Irino, F., Yoneyama, N., Fujimura, T. and Ashihara, H.
    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: 56-60 (2003). [PMID: 12860386]
  3. Uefuji, H., Ogita, S., Yamaguchi, Y., Koizumi, N. and Sano, H.
    Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants.
    Plant Physiol. 132: 372-380 (2003). [PMID: 12746542]
  4. Yoneyama, N., Morimoto, H., Ye, C.-X., Ashihara, H., Mizuno, K. and Kato, M.
    Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme.
    Mol. Genet. Genomics 275: 125-135 (2006). [PMID: 16333668]

[EC created 2007]