title: Molecular cloning and functional analysis of serotonin N-acetyltransferase from the cyanobacterium Synechocystis sp. PCC 6803.
abstract: 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 Km and Vmax were 823 μm 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.
authors: Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors: Yeong
authors: Y
authors: Byeon
authors: Kyungjin
authors: K
authors: Lee
authors: Youn-Il
authors: YI
authors: Park
authors: Sangkyu
authors: S
authors: Park
authors: Kyoungwhan
authors: K
authors: Back
mesh_terms: D047068:Arylalkylamine N-Acetyltransferase / Q000235:genetics* / Q000378:metabolism*; D007700:Kinetics; D008550:Melatonin / Q000378:metabolism; D046939:Synechocystis / Q000201:enzymology*
chemical_list: D047068:Arylalkylamine N-Acetyltransferase; D008550:Melatonin
keywords: Synechocystis sp. PCC 6803; kinetic analysis; melatonin; serotonin N-acetyltransferase