KEGG   ORTHOLOGY: K12729
Entry
K12729            Tight     KO                                     

Name
XMT
Definition
7-methylxanthosine synthase [EC:2.1.1.158]
Pathway
ko00232  Caffeine metabolism
ko01100  Metabolic pathways
ko01110  Biosynthesis of secondary metabolites
Brite
KEGG Orthology (KO) [BR:ko00001]
 09100 Metabolism
  09110 Biosynthesis of other secondary metabolites
   00232 Caffeine metabolism
    K12729  XMT; 7-methylxanthosine synthase
Enzymes [BR:ko01000]
 2. Transferases
  2.1  Transferring one-carbon groups
   2.1.1  Methyltransferases
    2.1.1.158  7-methylxanthosine synthase
     K12729  XMT; 7-methylxanthosine synthase
Other DBs
RN: R07917
Genes
AG: ABD90685(XMT) BAB39215(XMT)
Reference
  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 132:372-80 (2003)
DOI:10.1104/pp.102.019679
  Sequence
Reference
  Authors
McCarthy AA, Biget L, Lin C, Petiard V, Tanksley SD, McCarthy JG
  Title
Cloning, expression, crystallization and preliminary X-ray analysis of the XMT and DXMT N-methyltransferases from Coffea canephora (robusta).
  Journal
Acta Crystallogr Sect F Struct Biol Cryst Commun 63:304-7 (2007)
DOI:10.1107/S1744309107009268
  Sequence

KEGG   ENZYME: 2.1.1.158
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
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)
R07917
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
ec00232  Caffeine metabolism
ec01100  Metabolic pathways
ec01110  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 49:2221-2222 (1985)
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 547:56-60 (2003)
DOI:10.1016/S0014-5793(03)00670-7
  Sequence
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 132:372-80 (2003)
DOI:10.1104/pp.102.019679
  Sequence
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 275:125-35 (2006)
DOI:10.1007/s00438-005-0070-z
Other DBs
ExplorEnz - The Enzyme Database: 2.1.1.158
IUBMB Enzyme Nomenclature: 2.1.1.158
ExPASy - ENZYME nomenclature database: 2.1.1.158
BRENDA, the Enzyme Database: 2.1.1.158

KEGG   REACTION: R07917
Entry
R07917                      Reaction                               

Name
S-adenosyl-L-methionine:xanthosine N7-methyltransferase
Definition
S-Adenosyl-L-methionine + Xanthosine <=> S-Adenosyl-L-homocysteine + 7-Methylxanthosine
Equation
Reaction class
RC00003  C00019_C00021
RC00336  C01762_C16352
Enzyme
Pathway
rn00232  Caffeine metabolism
rn01100  Metabolic pathways
rn01110  Biosynthesis of secondary metabolites
Orthology
K12729  7-methylxanthosine synthase [EC:2.1.1.158]
Other DBs
RHEA: 15028

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