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 ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 7-methylxanthosine

7-methylxanthosine synthase
Identifiers
EC no.	2.1.1.158
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Search PMC articles PubMed articles NCBI proteins

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 (7): 2221–2222. doi:10.1271/bbb1961.49.2221.
• Mizuno K, Kato M, Irino F, Yoneyama N, Fujimura T, Ashihara H (July 2003). "The first committed step reaction of caffeine biosynthesis: 7-methylxanthosine synthase is closely homologous to caffeine synthases in coffee (Coffea arabica L.)". FEBS Letters. 547 (1–3): 56–60. doi:10.1016/S0014-5793(03)00670-7. PMID 12860386.
• Uefuji H, Ogita S, Yamaguchi Y, Koizumi N, Sano H (May 2003). "Molecular cloning and functional characterization of three distinct N-methyltransferases involved in the caffeine biosynthetic pathway in coffee plants". Plant Physiology. 132 (1): 372–80. doi:10.1104/pp.102.019679. PMC 166982. PMID 12746542.
• Yoneyama N, Morimoto H, Ye CX, Ashihara H, Mizuno K, Kato M (February 2006). "Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme". Molecular Genetics and Genomics. 275 (2): 125–35. doi:10.1007/s00438-005-0070-z. PMID 16333668.