title: Cloning and characterization of a serotonin N-acetyltransferase from a gymnosperm, loblolly pine (Pinus taeda).
abstract: Serotonin N-acetyltransferase (SNAT) is the penultimate enzyme in melatonin biosynthesis in both animals and plants. SNAT catalyzes serotonin into N-acetylserotonin, an immediate precursor for melatonin biosynthesis by N-acetylserotonin methyltransferase (ASMT). We cloned the SNAT gene from a gymnosperm loblolly pine (Pinus teada). The loblolly pine SNAT (PtSNAT) gene encodes 255 amino acids harboring a transit sequence with 67 amino acids and shows 67% amino acid identity with rice SNAT when comparing the mature polypeptide regions. Purified recombinant PtSNAT showed peak activity at 55°C with the K(m) (428 μM) and Vmax (3.9 nmol/min/mg protein) values. As predicted, PtSNAT localized to chloroplasts. The SNAT mRNA was constitutively expressed in all tissues, including leaf, bud, flower, and pinecone, whereas the corresponding protein was detected only in leaf. In accordance with the exclusive SNAT protein expression in leaf, melatonin was detected only in leaf at 0.45 ng per gram fresh weight. Sequence and phylogenetic analysis indicated that the gymnosperm PtSNAT had high homology with SNATs from all plant phyla (even with cyanobacteria), and formed a clade separated from the angiosperm SNATs, suggestive of direct gene transfer from cyanobacteria via endosymbiosis.
authors.affiliation: Department of Biotechnology, Bioenergy Research Center, Chonnam National University, Gwangju, Korea.
authors.forename: Sangkyu
authors.initials: S
authors.lastname: Park
authors.forename: Yeong
authors.initials: Y
authors.lastname: Byeon
authors.forename: Hyoung Yool
authors.initials: HY
authors.lastname: Lee
authors.forename: Young-Soon
authors.initials: YS
authors.lastname: Kim
authors.forename: Taeho
authors.initials: T
authors.lastname: Ahn
authors.forename: Kyoungwhan
authors.initials: K
authors.lastname: Back
mesh_terms: D000595:Amino Acid Sequence; D047068:Arylalkylamine N-Acetyltransferase / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D018744:DNA, Plant; D010802:Phylogeny; D028223:Pinus / Q000201:enzymology / Q000235:genetics*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D018744:DNA, Plant; D047068:Arylalkylamine N-Acetyltransferase
keywords: Pinus taeda; loblolly pine; melatonin; serotonin N-acetyltransferase; subcellular location