Effect of pyruvate and its analogs on the thiamine pyrophosphate binding in the active center of muscle pyruvate dehydrogenase

Khailova, L.; Severin, S.; Hübner, G.; Neef, H.; Schellenberger, A.

Авторы: Khailova LS, Severin SE, Hübner G., Neef H., Schellenberger A.
Журнал: FEBS Letters
Том: 139
Номер: 1
Год издания: 1982
Издательство: Elsevier BV
Местоположение издательства: Netherlands
Первая страница: 49
Последняя страница: 52
DOI: 10.1016/0014-5793(82)80484-5
Аннотация: The pyruvate decarboxylating component (PDC) of the pyruvate dehydrogenase complex from pigeon breast muscle (EC 1.2.4.1) catalyzes the oxidative decarboxylation of pyruvate in the presence of thi- amine pyrophosphate (TPP), Mg2+ and non-physiolog- ical oxidants, such as 2,6-dichlorophenol-indophenol (DCPIP), with the formation of C02, acetate and the reduced dye [ 1,2]. The ‘cwcarbanion’-intermediate (CI) formed in the enzyme reaction after the decarboxyla- tion of the TPP-bound substrate is oxidized by the dye [3]. The protonated intermediate (2+hydroxyethyl)- TPP, HETPP) shows no significant reactivity with DCPIP. If cu-ketobutyrate is used as substrate of the decar- boxylating component, a rapid inactivation of the enzyme occurs after a short period of high activity [4]. On principle this effect can be observed also with pyruvate but in a much smaller degree than in the case of the substrate analog (fig.1). This inactivation reaction proceeds only in the presence of TPP, Mg2+ and DCPIP, suggesting the formation of a relatively stable non-productive complex between the protein component and the oxidized species of the 2-(o-hy- droxypropyl)TPPcarbanion (HPTPP(-)) [S]. This paper confirms that in the course of the inac- tivation reaction, an inactive complex between the protein and a TPPderivative is produced, which is formed in the oxidation reaction with DCPIP. The carbanion intermediate with its reduced positive charge on the thiazolium ring is bound more tightly to the active center than the coenzyme itself.
Добавил в систему: Хайлова Людмила Самуиловна

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