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Molecular cloning of a plant N ‐acetylserotonin methyltransferase and its expression characteristics in rice
Author(s) -
Kang Kiyoon,
Kong Kyoungjin,
Park Sangkyu,
Natsagdorj Uyanga,
Kim Young Soon,
Back Kyoungwhan
Publication year - 2011
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2010.00841.x
Subject(s) - melatonin , biology , methyltransferase , recombinant dna , enzyme , open reading frame , escherichia coli , microbiology and biotechnology , methionine , molecular cloning , biochemistry , amino acid , methylation , gene expression , peptide sequence , endocrinology , gene
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.