title: Substrate specificity of N-methyltransferase involved in purine alkaloids synthesis is dependent upon one amino acid residue of the enzyme.
abstract: Caffeine (1,3,7-trimethylxanthine) and theobromine (3,7-dimethylxanthine) are the major purine alkaloids in plants. To investigate the diversity of N-methyltransferases involved in purine alkaloid biosynthesis, we isolated the genes homologous for caffeine synthase from theobromine-accumulating plants. The predicted amino acid sequences of N-methyltransferases in theobromine-accumulating species in Camellia were more than 80% identical to caffeine synthase in C. sinensis. However, there was a little homology among the N-methyltransferases between Camellia and Theobroma. The recombinant enzymes derived from theobromine-accumulating plants had only 3-N-methyltransferase activity. The accumulation of purine alkaloids was, therefore, dependent on the substrate specificity of N-methyltransferase determined by one amino acid residue in the central part of the protein.
authors.affiliation: Graduate School of Humanities and Sciences, Ochanomizu University, Otsuka, Bunkyo-ku, Tokyo, Japan.
authors.forename: Naho
authors.initials: N
authors.lastname: Yoneyama
authors.forename: Hanayo
authors.initials: H
authors.lastname: Morimoto
authors.forename: Chuang-Xing
authors.initials: CX
authors.lastname: Ye
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ashihara
authors.forename: Kouichi
authors.initials: K
authors.lastname: Mizuno
authors.forename: Misako
authors.initials: M
authors.lastname: Kato
mesh_terms: D000470:Alkaloids / Q000096:biosynthesis* / Q000737:chemistry; D000595:Amino Acid Sequence; D001483:Base Sequence; D002099:Cacao / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D002110:Caffeine / Q000096:biosynthesis; D028244:Camellia / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D018744:DNA, Plant / Q000235:genetics; D015723:Gene Library; D017343:Genes, Plant; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010802:Phylogeny; D010957:Plasmids / Q000235:genetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D013805:Theobromine / Q000096:biosynthesis
chemical_list: D000470:Alkaloids; D018744:DNA, Plant; D011994:Recombinant Proteins; D002110:Caffeine; D008780:Methyltransferases; C120479:caffeine synthase; D013805:Theobromine