Studies on Plant Aspartate Transcarbamylase Purification and Properties of the Enzyme from Mung-Bean (Phaseolus aureus) Seedlings

Achar, BS and Savithri, HS and Vaidyanathan, CS and Rao, NA (1974) Studies on Plant Aspartate Transcarbamylase Purification and Properties of the Enzyme from Mung-Bean (Phaseolus aureus) Seedlings. In: European Journal of Biochemistry, 47 (1). pp. 15-22.

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Abstract

Aspartate transcarbamylase is purified from mung bean seedlings by a series of steps involving manganous sulphate treatment, ammonium sulphate fractionation, DEAE-cellulose chromatography, followed by a second ammonium sulphate fractionation and finally gel filtration on Sephadex-G 100. The enzyme is homogeneous on ultracentrifugation and on polyacrylamide gel electrophoresis. It functions optimally at 55°C. It has two pH optima, one at 8.0 and the other at 10.2. The enzyme follows Michaelis-Menten kinetics with l-aspartate as the variable substrate. However, it exhibits sigmoid saturation curves at both the pH optima when the concentration of carbamyl phosphate is varied. The enzyme is allosterically inhibited by UMP at both the pH optima. Increasing phosphorylation of the uridine nucleotide decreases the inhibitory effect. The enzyme is desensitized to inhibition by UMP on treatment with p-hydroxymercuribenzoate, gel electrophoresis indicating that the enzyme is dissociated by this treatment; the dissociated enzyme can be reassociated by treatment with 2-mercaptoethanol. The properties of the mung bean enzyme are compared with the enzyme from other sources.

Item Type:	Journal Article
Publication:	European Journal of Biochemistry
Publisher:	John Wiley and Sons
Additional Information:	Copyright of this article belongs to John Wiley and Sons.
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	29 Jan 2010 07:05
Last Modified:	23 Feb 2012 06:34
URI:	http://eprints.iisc.ac.in/id/eprint/23394

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