Transferases;
Transferring one-carbon groups;
Methyltransferases
BRITE hierarchy

S-adenosyl-L-methionine:xanthosine N7-methyltransferase

S-adenosyl-L-methionine + xanthosine = S-adenosyl-L-homocysteine + 7-methylxanthosine [RN:R07917]

R07917
Reaction

S-adenosyl-L-methionine [CPD:C00019];
xanthosine [CPD:C01762]

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.

EC 2.1.1.158 created 2007

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  [PMID:12860386]

Mizuno K, Kato M, Irino F, Yoneyama N, Fujimura T, 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)
DOI:10.1016/S0014-5793(03)00670-7

[ag:BAB39215]

3  [PMID:12746542]

Uefuji H, Ogita S, Yamaguchi Y, Koizumi N, Sano H

Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants.

Plant Physiol 132:372-80 (2003)
DOI:10.1104/pp.102.019679

[ag:BAB39215]

4  [PMID:16333668]

Yoneyama N, Morimoto H, Ye CX, Ashihara H, Mizuno K, 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 275:125-35 (2006)
DOI:10.1007/s00438-005-0070-z