KEGG   ENZYME: 2.1.1.158Help
Entry
EC 2.1.1.158                Enzyme                                 

Name
7-methylxanthosine synthase;
xanthosine methyltransferase;
XMT;
xanthosine:S-adenosyl-L-methionine methyltransferase;
CtCS1;
CmXRS1;
CaXMT1;
S-adenosyl-L-methionine:xanthosine 7-N-methyltransferase
Class
Transferases;
Transferring one-carbon groups;
Methyltransferases
BRITE hierarchy
Sysname
S-adenosyl-L-methionine:xanthosine N7-methyltransferase
Reaction(IUBMB)
S-adenosyl-L-methionine + xanthosine = S-adenosyl-L-homocysteine + 7-methylxanthosine [RN:R07917]
Reaction(KEGG)
Substrate
S-adenosyl-L-methionine [CPD:C00019];
xanthosine [CPD:C01762]
Product
S-adenosyl-L-homocysteine [CPD:C00021];
7-methylxanthosine [CPD:C16352]
Comment
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.
History
EC 2.1.1.158 created 2007
Pathway
Caffeine metabolism
Metabolic pathways
Biosynthesis of secondary metabolites
Orthology
K12729  
7-methylxanthosine synthase
Reference
1
  Authors
Negishi, O., Ozawa, T. and Imagawa, H.
  Title
The role of xanthosine in the biosynthesis of caffeine in coffee plants.
  Journal
Agric. Biol. Chem. 49 (1985) 2221-2222.
Reference
2  [PMID:12860386]
  Authors
Mizuno K, Kato M, Irino F, Yoneyama N, Fujimura T, Ashihara H.
  Title
The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.).
  Journal
FEBS. Lett. 547 (2003) 56-60.
  Sequence
[up:Q9AVK0]
Reference
3  [PMID:12746542]
  Authors
Uefuji H, Ogita S, Yamaguchi Y, Koizumi N, Sano H.
  Title
Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants.
  Journal
Plant. Physiol. 132 (2003) 372-80.
  Sequence
[up:Q9AVK0]
Reference
4  [PMID:16333668]
  Authors
Yoneyama N, Morimoto H, Ye CX, Ashihara H, Mizuno K, Kato M.
  Title
Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme.
  Journal
Mol. Genet. Genomics. 275 (2006) 125-35.
Other DBs
ExplorEnz - The Enzyme Database: 
IUBMB Enzyme Nomenclature: 
ExPASy - ENZYME nomenclature database: 
BRENDA, the Enzyme Database: 

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