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Purification and physicochemical, kinetic and immunological properties of allosteric serine hydroxymethyltransferase from monkey liver.

Ramesh, KS and Rao, N Appaji (1980) Purification and physicochemical, kinetic and immunological properties of allosteric serine hydroxymethyltransferase from monkey liver. In: Biochemical Journal, 187 (3). pp. 623-636.

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Abstract

The homogeneous serine hydroxymethyltransferase purified from monkey liver, by the use of Blue Sepharose affinity chromatography, exhibited positive homotropic co-operative interactions (h = 2.5) with tetrahydrofolate and heterotropic interactions with L-serine and nicotinamide nucleotides. The enzyme had an unusually high temperature optimum of 60 degrees C and was protected against thermal inactivation by L-serine. The allosteric effects were abolished when the monkey liver enzyme was purified by using a heat-denaturation step in the presence of L-serine, a procedure adopted by earlier workers for the purification of this enzyme from mammalian and bacterial sources. The enzyme activity was inhibited completely by N5-methyltetrahydrofolate, N5-formyltetrahydrofolate, dichloromethotrexate, aminopterin and D-cycloserine, whereas methotrexate and dihydrofolate were partial inhibitors. The insoluble monkey liver enzyme-antibody complex was catalytically active and failed to show positive homotropic co-operative interactions with tetrahydrofolate (h = 1) and heterotropic interactions with NAD+. The enzyme showed a higher heat-stability in a complex with its antibody than as the free enzyme. These results highlight the pitfalls in using a heat-denaturation step in the purification of allosteric enzymes.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to the Portland Press.
Department/Centre: Division of Biological Sciences > Biochemistry
Date Deposited: 05 Feb 2010 10:36
Last Modified: 19 Sep 2010 05:39
URI: http://eprints.iisc.ernet.in/id/eprint/21818

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