Some properties of shikimate: NADP oxidoreductase produced in sweet potato root tissue after slicing |
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Authors: | KOJIMA, MINEO MINAMIKAWA, TAKAO URITANI, IKUZO |
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Affiliation: | Laboratory of Biochemistry and Institute for Biochemical Regulation, Faculty of Agriculture, Nagoya University Nagoya, Japan |
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Abstract: | The activity of shikimate: NADP oxidoreductase [EC 1. 1. 1.25] in sweet potato root tissue increased soon after slicing.Enzyme preparations obtained from both sliced tissue and fromfresh tissue probably contained a single enzyme component, andthey showed identical chromatographical behaviour. Km values of the enzyme for NADP and shikimate were 1.0x104Mand 1.3 x 103M, respectively. Enzyme activity was potentlyinhibited by SH-inhibitors such as p-chloromercuribenzoate andoxidized glutathione. Enzyme activity was affected neither by mononucleotides suchas ATP, ADP and AMP, divalent cations, Mg++, Ca++ and Mn++,nor by metabolites such as tryptophan, phenylalanine, tyrosineand t-cinnamic acid which are involved in aromatic compoundsyntheses. The enzyme rapidly lost its activity. This inactivation reactionshowed a time course consisting of two steps of the first-orderreaction. The inactivated enzyme preparation was not reactivatedby thiol compounds such as cysteine, 2-mercaptoethanol and glutathione,although these reagents, to a certain extent, protected theenzyme from inactivation. The results suggest that denaturationof the enzyme protein was involved in inactivation of the enzyme. 1Part 74 of the phytopathological chemistry of sweet potatowith black rot and injury.2Present address: Department of Biology, Faculty of Science,Tokyo Metropolitan University, Setagaya-ku, Tokyo. (Received August 5, 1968; ) |
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