Volume 1, Issue 1 pp. 45-56
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CHARACTERIZATION OF PHYTASE OF BEANS (PHASEOLUS VULGARIS)

RUTH CHANG

RUTH CHANG

Department of Nutritional Sciences University of California Berkeley, California 94720

Insitute of Medical Sciences, Pacific Medical Center, 2200 Webster Street, San Francisco, California 94115

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SIGMUND SCHWIMMER

SIGMUND SCHWIMMER

Western Regional Research Laboratory Agricultural Research Service U. S. Department of Agriculture Albany, California 94710

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First published: January 1977
Citations: 17

Abstract

Phytase from California Small White beans was extracted, concentrated and enriched by heat treatment and ammonium sulfate fractionation. Crude enzyme fractions tenaciously retained endogenous phytate which could be removed by autolysis at 45°C and pH 5.2. Characterization of the phytase preparation showed: (1) increase in activity with increasing temperature from 37 to 60°C, (2) an activation energy of approximately 9,200 cal/mole for the hydrolysis of inositol hexaphosphate; (3) pH optimum of 5.2; (4) a Km value of 2.22 × 10-4M; (5) apparently partial inhibition at high substrate concentrations; (6) fully competitive inhibition by one of the reaction products, inorganic phosphate, with Ki=3.1 × 104M. These properties and kinetic constants are comparable to those reported for phytase preparations from similar sources and they adequately account for in situ autolytic loss of phytic acid from these beans.

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