Regulation of Ammonium Ion Salvage and Enhancement of the Storage Protein Contents of Corn, Sweet Potato, and Yam Tuber by Nα-(Carboxymethyl)Chitosan Application

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Journal of Agricultural and Food Chemistry


The biochemical approach to storage protein enhancement via NH4+ ion metabolism was investigated by treatment of growing yam tuber, sweet potato, and corn with N-(carboxymethyl)chitosan (NCMC). Application of NCMC to yam tuber gave rise to α-ketoglutarate (αKG)-dependent inhibition of the glutamate synthase (GOGAT) with an inhibition constant (Ki) of 3 mM but relieved the αKG-dependent inhibition of the glutamate dehydrogenase (GDH), with a concomitant 270% increase of the storage protein content. In sweet potato, NCMC application gave rise to glutamate-dependent inhibition of the glutamine synthetase (GS) with Ki of 15 mM but relieved the inhibition of the GDH by high αKG concentrations, with a concomitant doubling of the storage protein contents. In corn, NCMC application also gave rise to aKG-dependent inhibition of the GOGAT with Ki of 0.5 mM but relieved the αKGdependent inhibition of the GDH, with a concomitant doubling of the storage protein content. NCMC treatment also reduced the levels of some of the high molecular weight polypeptides (deaminating) while it increased the levels of some of the low molecular weight polypeptides (aminating) of GDH. Therefore, NCMC enhanced the storage protein contents of the crops by enhancing NH4+ ion salvage. © 1992, American Chemical Society. All rights reserved.

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