REAL

Transient kinetic studies reveal isomerisation steps along the kinetic pathway of Thermus thermophilus 3-Isopropylmalate Dehydrogenase.

Gráczer, Eva and Lionne, Corinne and Závodszky, Péter and Chaloin, Laurent and Vas, Mária (2013) Transient kinetic studies reveal isomerisation steps along the kinetic pathway of Thermus thermophilus 3-Isopropylmalate Dehydrogenase. The FEBS journal, 280 (8). pp. 1764-72. ISSN 1742-4658

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Abstract

To identify the rate limiting step(s) of 3-isopropylmalate dehydrogenase (IPMDH) catalysed reaction, time courses of NADH production were followed by stopped flow (SF) and quenched flow (QF). The steady state k(cat) and K(m) values did not vary between 0.1 and 20 µM enzyme concentrations. A burst phase of the NADH formation was shown by QF, indicating that the rate limiting step occurs after the redox step. The kinetics of protein conformational change(s) induced by Mg·IPM (the complex of 3-isopropylmalate with Mg(2+) ) were followed using a FRET (fluorescence resonance energy transfer) signal between protein tryptophan(s) and the bound NADH. A reaction scheme was proposed by incorporating the rate constant of a fast protein conformational change (possibly domain closure) derived from the separately recorded time-dependent formation of FRET. The rate limiting step seems to be another slower conformational change (domain opening) that allows the product release.

Item Type: Article
Subjects: Q Science / természettudomány > Q1 Science (General) / természettudomány általában
Depositing User: Dr. Maria Vas
Date Deposited: 06 Mar 2013 16:22
Last Modified: 13 May 2016 08:01
URI: http://real.mtak.hu/id/eprint/4364

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