Aluminum: a pH-dependent inhibitor of NADP-isocitrate dehydrogenase from porcine heart |
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Authors: | Masataka Yoshino Keiko Murakami |
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Institution: | (1) Department of Genetics, Institute for Developmental Research, Kasugai Aichi Prefectural Colony, Kamiya-cho 713-8, 480-03 Kasugai, Aichi, Japan;(2) Inazawa Junior College, 480-03 Inazawa, Aichi, Japan |
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Abstract: | Aluminum showed a pH-dependent inhibitory effect on NADP-isocitrate dehydrogenase from porcine heart. Aluminum ions (Al3+) acted as a partial competitive inhibitor of the enzyme with respect to the substratethreo-Ds-isocitrate and inhibited the enzyme non-competitively with respect to NADP at pH 6.85. Fractional velocity plot analysis showed theK
i of the enzyme for aluminum ions to be 0.88m. When pH was elevated to 8.0, aluminum ions, which occur as a form of the Al(OH)4
– anion, acted as partial uncompetitive and non-competitive inhibitors of the enzyme with respect to the substrates isocitrate and NADP, respectively. TheK
i of the enzyme was determined to be 5.64 m at pH 8.0 by fractional velocity plot analysis. The inhibition of NADP-isocitrate dehydrogenase by two forms of aluminum ions may explain aluminum toxicity in various tissues and organs. |
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Keywords: | aluminum inhibition NADP-isocitrate dehydrogenase |
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