Pyridine salvage and nicotinic acid conjugate synthesis in leaves of mangrove species |
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Authors: | Hiroshi Ashihara Yuling Yin Shin Watanabe |
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Institution: | a Department of Biological Sciences, Graduate School of Humanities and Sciences, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan b Iriomote Station, Tropical Biosphere Research Center, University of Ryukyus, 870, Uehara, Taketomi-cho, Yaeyama-gun, Okinawa 907-1541, Japan |
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Abstract: | The metabolic fate of carbonyl-14C]nicotinamide was surveyed in leaf disks of seven mangrove species, Bruguiera gymnorrhiza, Rhizophora stylosa, Kandeliaobovata, Sonneratia alba, Pemphis acidula, Lumnitzera racemosa and Avicennia marina, with and without 250 mM NaCl. Uptake of 14C]nicotinamide by leaf disks was stimulated by 250 mM NaCl in K. candel, R. stylosa, A. marina and L. racemosa. Carbonyl-14C]nicotinamide was converted to nicotinic acid and was utilised for the synthesis of nucleotides and nicotinic acid conjugates. Formation of nicotinic acid by the deaminase reaction was rapid; there was little accumulation of nicotinamide in the disks 3 h after administration. Radioactivity from carbonyl-14C]nicotinamide was incorporated into pyridine nucleotides (mainly NAD and NADP) in all mangrove leaves, and the rates varied from 2% (in L. racemosa) to 15% (S. alba) of the total radioactivity taken up. NaCl generally reduced nicotinic acid salvage for NAD and NADP. In all mangrove leaf disks, the most heavily labelled compounds (up to 70% of total radioactivity) were trigonelline (N-methylnicotinic acid) and/or nicotinic acid N-glucoside. Trigonelline was formed in all mangrove plants, but N-glucoside synthesis was found only in leaves of A. marina and K. obovata. In A. marina, incorporation of radioactivity into N-glucoside (51%) was much greater than incorporation into trigonelline (2%). In general, NaCl stimulates the synthesis of these pyridine conjugates. The rate of decarboxylation of nicotinic acid in roots of A. marina seedlings was much greater than for the corresponding reaction observed in leaves. |
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Keywords: | NaAD nicotinic acid adenine dinucleotide NaG nicotinic acid N-glucoside NaMN nicotinic acid mononucleotide NMN nicotinamide mononucleotide NR nicotinamide riboside SAM S-adenosylmethionine SAH S-adenosylhomocysteine UDPG UDP-glucose |
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