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Cloning and characterization of a serotonin N ‐acetyltransferase from a gymnosperm, loblolly pine ( Pinus taeda )
Author(s) -
Park Sangkyu,
Byeon Yeong,
Lee Hyoung Yool,
Kim YoungSoon,
Ahn Taeho,
Back Kyoungwhan
Publication year - 2014
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.12174
Subject(s) - gymnosperm , biology , amino acid , biochemistry , gene , rubisco , botany
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 ( Pt SNAT ) 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 Pt SNAT showed peak activity at 55°C with the K m (428 μ m ) and V max (3.9 nmol/min/mg protein) values. As predicted, Pt SNAT 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 Pt SNAT had high homology with SNAT s from all plant phyla (even with cyanobacteria), and formed a clade separated from the angiosperm SNAT s, suggestive of direct gene transfer from cyanobacteria via endosymbiosis.