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Molecular cloning and functional analysis of serotonin N ‐acetyltransferase from the cyanobacterium Synechocystis sp. PCC 6803
Author(s) -
Byeon Yeong,
Lee Kyungjin,
Park YounIl,
Park Sangkyu,
Back Kyoungwhan
Publication year - 2013
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/jpi.12080
Subject(s) - biochemistry , biology , enzyme , serotonin , cloning (programming) , gene , acetyltransferase , acetylation , receptor , computer science , programming language
Serotonin N ‐acetyltransferase (SNAT) catalyzes conversion of serotonin into N ‐acetylserotonin, which is a direct precursor for melatonin biosynthesis in all organisms. Molecular cloning of plant SNAT from rice led to a screening for SNAT homolog genes in other species. We identified a cyanobacterium SNAT ‐like gene ( cSNAT ) that showed 56% amino acid homology with the rice SNAT. To confirm whether cSNAT encoded SNAT enzyme activity, we expressed cSNAT DNA in Escherichia coli and purified the cSNAT protein as a C‐terminal His‐tagged form. The purified cSNAT protein exhibited SNAT enzyme activities, transferring the acetyl group into either serotonin or tryptamine substrates. The optimum temperature was 55°C, but it was still highly active at 70°C, suggesting that cSNAT is a thermotolerant enzyme. The K m and V max were 823 μ m and 1.6 nmol/min/mg protein, respectively. The cSNAT gene is highly conserved in all cyanobacterial taxa and seems to be an origin of SNAT in higher plants. The thermotolerance of cSNAT suggests that melatonin plays a role in the response to high‐temperature stress. Further analysis of this role of melatonin in higher plants is needed.

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