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Purification and regulation of aspartate transcarbamylase from germinated mung bean (Vigna radiata) seedlings

Prasad, PV and Appaji Rao, N (1984) Purification and regulation of aspartate transcarbamylase from germinated mung bean (Vigna radiata) seedlings. In: Journal of Bioscience, 6 (2). pp. 233-248.

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Aspartate transcarbamylase (EC was purified to homogeniety from germinated mung bean seedlings by treatment with carbamyl phosphate. The purified enzyme was a hexamer with a subunit molecular weight of 20,600. The enzyme exhibited multiple activity bands on Polyacrylamide gel electrophoresis, which could be altered by treatment with carbamyl phosphate or UMP indicating that the enzyme was probably undergoing reversible association or dissociation in the presence of these effectors. The carbamyl phosphate stabilized enzyme did not exhibit positive homotropic interactions with carbamyl phosphate and hysteresis. The enzyme which had not been exposed to carbamyl phosphate showed a decrease in specific activity with a change in the concentration of both carbamyl phosphate and protein. The carbamyl phosphate saturation and U M P inhibition patterns were complex with a maximum and a plateau region. The partially purified enzyme also exhibited hysteresis and the hysteretic response, a function of protein concentration, was abolished by preincubation with carbamyl phosphate and enhanced by preincubation with UMP. All these observations are compatible with a postulation that the enzyme activity may be regulated by slow reversible association-dissociation dependent on the interaction with allosteric ligands.

Item Type: Journal Article
Publication: Journal of Bioscience
Publisher: Indian academy of sciences
Additional Information: Copyright for this article belongs to Indian academy of sciences.
Keywords: Aspartate transcarbamylase; mung bean; purification; regulation; hysteresis; association-dissociation
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 28 Jan 2010 07:32
Last Modified: 19 Sep 2010 05:43
URI: http://eprints.iisc.ac.in/id/eprint/22838

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