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Plant and Cell Physiology, 1969, Vol. 10, No. 2 245-257
© 1969

Article

Some properties of shikimate: NADP oxidoreductase produced in sweet potato root tissue after slicing1

MINEO KOJIMA, TAKAO MINAMIKAWA2 and IKUZO URITANI

Laboratory of Biochemistry and Institute for Biochemical Regulation, Faculty of Agriculture, Nagoya University Nagoya, Japan

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 from fresh tissue probably contained a single enzyme component, and they showed identical chromatographical behaviour.

Km values of the enzyme for NADP and shikimate were 1.0x10–4M and 1.3 x 10–3M, respectively. Enzyme activity was potently inhibited by SH-inhibitors such as p-chloromercuribenzoate and oxidized glutathione.

Enzyme activity was affected neither by mononucleotides such as ATP, ADP and AMP, divalent cations, Mg++, Ca++ and Mn++, nor by metabolites such as tryptophan, phenylalanine, tyrosine and t-cinnamic acid which are involved in aromatic compound syntheses.

The enzyme rapidly lost its activity. This inactivation reaction showed a time course consisting of two steps of the first-order reaction. The inactivated enzyme preparation was not reactivated by thiol compounds such as cysteine, 2-mercaptoethanol and glutathione, although these reagents, to a certain extent, protected the enzyme from inactivation. The results suggest that denaturation of the enzyme protein was involved in inactivation of the enzyme.

1Part 74 of the phytopathological chemistry of sweet potato with 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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