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J. Biol. Chem., Vol. 283, Issue 9, 5344-5354, February 29, 2008

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Amino Acids Allosterically Regulate the Thiamine Diphosphate-dependent -Keto Acid Decarboxylase from Mycobacterium tuberculosis^*

From the Institute of Biochemistry and Biotechnology, Faculty for Biological Sciences, Martin-Luther-University Halle-Wittenberg, 06120 Halle (Saale), Germany

The gene rv0853c from Mycobacterium tuberculosis strain H37Rv codes for a thiamine diphosphate-dependent -keto acid decarboxylase (MtKDC), an enzyme involved in the amino acid degradation via the Ehrlich pathway. Steady state kinetic experiments were performed to determine the substrate specificity of MtKDC. The mycobacterial enzyme was found to convert a broad spectrum of branched-chain and aromatic -keto acids. Stopped-flow kinetics showed that MtKDC is allosterically activated by -keto acids. Even more, we demonstrate that also amino acids are potent activators of this thiamine diphosphate-dependent enzyme. Thus, metabolic flow through the Ehrlich pathway can be directly regulated at the decarboxylation step. The influence of amino acids on MtKDC catalysis was investigated, and implications for other thiamine diphosphate-dependent enzymes are discussed.

Received for publication, August 8, 2007 , and in revised form, December 13, 2007.

^* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The on-line version of this article (available at http://www.jbc.org) contains supplemental Figs. S1–S5 and Table S1.

¹ Both authors have contributed equally to the article.

² Supported by the Graduiertenkolleg of Sachsen-Anhalt.

³ Present address: Max-Delbrück Centre for Molecular Medicine, Protein Sample Production Facility, 13092 Berlin, Germany.

⁴ To whom correspondence should be addressed. Tel.: 49-345-5524829; Fax: 49-345-5527014; E-mail: stephan.koenig{at}biochemtech.uni-halle.de.

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