期刊
JOURNAL OF PINEAL RESEARCH
卷 57, 期 4, 页码 418-426出版社
WILEY
DOI: 10.1111/jpi.12181
关键词
5-methoxytryptamine; Arabidopsis thaliana; caffeic acid O-methyltransferase; serotonin N-acetyltransferase; substrate inhibition
资金
- Next-Generation BioGreen 21 Program [PJ00949105]
- Rural Development Administration
- Basic Research Program through the NRF of the Ministry of Education, Republic of Korea [2010-0020141]
- National Research Foundation of Korea [2010-0020141, 22A20130012880] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in melatonin biosynthesis. We cloned SNAT from Arabidopsis thaliana (AtSNAT) and functionally characterized this enzyme for the first time from dicotyledonous plants. Similar to rice SNAT, AtSNAT was found to localize to chloroplasts with peak enzyme activity at 45 degrees C (K-m, 309m; V-max, 1400pmol/min/mg protein). AtSNAT also catalyzed 5-methoxytryptamine (5-MT) into melatonin with high catalytic activity (K-m, 51m; V-max, 5300 pmol/min/mg protein). In contrast, Arabidopsis caffeic acid O-methyltransferase (AtCOMT) localized to the cytoplasm. Interestingly, AtCOMT can methylate serotonin into 5-MT with low catalytic activity (K-m, 3.396mm; V-max, 528 pmol/min/mg protein). These data suggest that serotonin can be converted into either N-acetylserotonin by SNAT or into 5-MT by COMT, after which it is metabolized into melatonin by COMT or SNAT, respectively. To support this hypothesis, serotonin was incubated in the presence of both AtSNAT and AtCOMT enzymes. In addition to melatonin production, the production of major intermediates depended on incubation temperatures; N-acetylserotonin was predominantly produced at high temperatures (45 degrees C), while low temperatures (37 degrees C) favored the production of 5-MT. Our results provide biochemical evidence for the presence of a serotonin O-methylation pathway in plant melatonin biosynthesis.
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