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Characteristics of the reverse reaction of NADP + ‐isocitrate dehydrogenase from castor bean seeds
Author(s) -
Satoh Yasohachi,
Nakamura Yasunori
Publication year - 1984
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1984.tb02799.x
Subject(s) - isocitrate dehydrogenase , chemistry , ricinus , carboxylation , enzyme , dehydrogenase , redox , medicinal chemistry , nuclear chemistry , biochemistry , catalysis , organic chemistry
The reductive carboxylation of α‐ketoglutarate by purified NADP + ‐isocitrate dehydrogenase (EC 1.1.1.42) from maturing castor bean seeds ( Ricinus communis L. ) has been characterized. The optimum pH for the reaction was 6.5, whereas pH 8.5 was optimum for oxidation of isocitrate (forward reaction). The enzyme utilized NADH as well as NADPH as the reducing agent in the reverse reaction, but only NADP + in the forward reaction. The Km values for NADPH and NADH were 0.044 and 2.8 m M respectively, and for α‐ketoglutarate and HCO 3 4.1 and 3.7 m M. The enzyme was activated by various cations including Mg 2+ , Mn 2+ , Co 2+ , Zn 2+ , Ni 2+ and Co 2+ . Km values for Mg 2+ Mn 2+ , Co 2+ and Zn 2+ were 12, 34, 37 and 49μ M respectively.