Structural and kinetic studies on the activators of succinate dehydrogenase

Susheela, L and Venkatesan, K and Ramasarma, T (1977) Structural and kinetic studies on the activators of succinate dehydrogenase. In: Biochimica et Biophysica Acta (BBA) - Enzymology, 480 (1). pp. 47-55.

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Abstract

1. 1. Diverse classes of compounds such as dicarboxylates, pyrophosphates, quinols and nitrophenols are known to activate mitochondrial succinate dehydrogenase (EC 1.3.99.1). Examples in each class — malonate, pyrophosphate, ubiquinol and 2,4-dinitrophenol — are selected for comparative studies on the kinetic constants and structural relationship. 2. 2. The activated forms of the enzyme obtained on preincubating mitochondria with the effectors exhibited Michaelian kinetics and gave doublereciprocal plots which are nearly parallel to that of the basal form. On activation, Km for the substrate also increased along with V. The effectors activated the enzyme at low concentrations and inhibited, in a competitive fashion, at high concentrations. The binding constant for activation was lower than that for inhibition for each effector. 3. 3. These compounds possess ionizable twin oxygens separated by a distance of Image and having fractional charges in the range of −0.26 to −0.74 e. The common twin-oxygen feature of the substrate and the effectors suggested the presence of corresponding counter charges in the binding domain. The competitive nature of effectors with the substrate for inhibition further indicated the close structural resemblance of the activation and catalytic sites.

Item Type:	Journal Article
Publication:	Biochimica et Biophysica Acta (BBA) - Enzymology
Publisher:	Elsevier Sceince
Additional Information:	Copyright for this article belongs to Elsevier Sceince.
Department/Centre:	Division of Chemical Sciences > Organic Chemistry Division of Biological Sciences > Biochemistry
Date Deposited:	20 Jan 2010 09:51
Last Modified:	19 Sep 2010 05:50
URI:	http://eprints.iisc.ac.in/id/eprint/24463

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