Formation of enzyme bound carbon dioxide in the reductive carboxylation of alpha-ketoglutarate by isocitrate dehydrogenase.

Ramakrishna, M. and Krishnaswamy, P. R. (1966) Formation of enzyme bound carbon dioxide in the reductive carboxylation of alpha-ketoglutarate by isocitrate dehydrogenase. Biochemical and Biophysical Research Communications, 25. pp. 378-382.

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Abstract

z* -1socitrate NADP oxidoredmctaae (E.C. 1.1.1.42) catalyses the reversible oxidative decarboxylation of imcitrate to alpha-ketoglutarate and carbon dioxide with the specific participation of NADP. No fme intermediate has been isolated in the overall reaction nor have attempts to demonstrate the existence of oxalosuecinic acid as a free intermediate or in the enzyme bound form been successful (Siebert et al., 1957; Plaut, 1963; Carsiotis, 1958). With large quantities of fairly purified enzyme and labeled carbon dioxide, we attempted to demonstrate enzyme bound oxalosuucinate in the overrall reverse reaction by use of the 'chase' technique successfully employed to demonstrate substrate binding for several enzymes (Krishnaswamy et al., 1962; NishI.mura et al., 1963; tierson and Moister, 1966). Enzyme bound carbon dioxide was demonstrated both in the presence and absence of NADP or of alpha-ketoglutarate; the extent of binding was significantly greater in the presence of NADP or of alpha-ketoglutarate. Enzyme bound oxalosuccinate was not found under these conditions. Prior incubation of carbon dioxide with the enzyme exerted a specific protective effect against inhibition by PCMR of the oxidation of isocitrate.

Item Type:	Article
Uncontrolled Keywords:	isocitrate, carbon dioxide, Isocitric dehydrogenase
Subjects:	500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 16 Enzyme Chemistry
Divisions:	Dept. of Biochemistry
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	02 Jun 2011 05:25
Last Modified:	28 Dec 2011 09:46
URI:	http://ir.cftri.res.in/id/eprint/4234

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