title: Molecular cloning of a plant N-acetylserotonin methyltransferase and its expression characteristics in rice.
abstract: N-acetylserotonin methyltransferase (ASMT), the last enzyme in the synthesis of melatonin, catalyzes N-acetylserotonin into melatonin. For the first time, we cloned ASMT from rice through the analysis of recombinant Escherichia coli harboring putative rice O-methyltransferase (OMT) cDNAs. In total, 18 full-length cDNAs, which show homology to wheat caffeic acid 3-O-methyltransferase, were expressed in E. coli and induced in the presence of N-acetylserotonin; we then analyzed the production of melatonin. Only recombinant E. coli line 15 showed melatonin synthesis; no other recombinant lines produced melatonin with the addition of N-acetylserotonin in E. coli culture. Line 15 clearly exhibited in vitro ASMT enzyme activity with 0.27 pkat/mg protein. ASMT enzyme activity was inhibited by various related compounds such as N-acetyltryptamine and N-acetyltyrosine. The open reading frame of ASMT consists of 364 amino acids possessing well-conserved motifs found in plant OMT such as S-adenosyl-L-methionine-binding and catalytic sites. Induction patterns of ASMT mRNA were well matched with the production of melatonin in rice leaves during senescence, as well as several stressors.
authors.affiliation: Department of Biotechnology, Interdisciplinary Program of Graduate School for Bioenergy and Biomaterials, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors.forename: Kiyoon
authors.initials: K
authors.lastname: Kang
authors.forename: Kyoungjin
authors.initials: K
authors.lastname: Kong
authors.forename: Sangkyu
authors.initials: S
authors.lastname: Park
authors.forename: Uyanga
authors.initials: U
authors.lastname: Natsagdorj
authors.forename: Young Soon
authors.initials: YS
authors.lastname: Kim
authors.forename: Kyoungwhan
authors.initials: K
authors.lastname: Back
mesh_terms: D000121:Acetylserotonin O-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D008550:Melatonin / Q000378:metabolism; D012275:Oryza / Q000201:enzymology* / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D010940:Plant Proteins; D000121:Acetylserotonin O-Methyltransferase; D008550:Melatonin