Purification and Characterization of NADP-Linked Isocitrate Dehydrogenase from the Copper-tolerant Wood-rotting Basidiomycete Fomitopsis palustris(Biochemistry & Molecular Biology)

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NADP-linked isocitrate dehydrogenase (EC 1. 1. 1. 42), a key enzyme of the tricarboxylic acid cycle, was purified 672-fold as a nearly homogeneous protein from the copper-tolerant wood-rotting basidiomycete Fomitopsis palustris. The purified enzyme, with a molecular mass of 115 kDa, consisted of two 55-kDa subunits, and had the K_m of 12.7, 2.9, and 23.9 μM for isocitrate, NADP, and Mg^<2+>, respectively, at the optimal pH of 9.0. The enzyme had maximum activity in the presence of Mg^<2+>, which also helped to prevent enzyme inactivation during the purification procedures and storage. The enzyme activity was competitively inhibited by 2-oxoglutarate (K_i, 127.0 μM). Although adenine nucleotides and other compounds, including some of the metabolic intermediates of glyoxylate and tricarboxylic acid cycles, had no or only slight inhibition, a mixture of oxaloacetate and glyoxylate potently inhibited the enzyme activity and the inhibition pattern was a mixed type.
社団法人日本農芸化学会の論文
2003-01-23