Amino acids allosterically regulate the thiamine diphosphate-dependent alpha-keto acid decarboxylase from Mycobacterium tuberculosis.
The gene rv0853c from Mycobacterium tuberculosis strain H37Rv codes for a thiamine diphosphate-dependent alpha-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 alpha-keto acids. Stopped-flow kinetics showed that MtKDC is allosterically activated by alpha-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.
Werther
Tobias
T
Institute of Biochemistry and Biotechnology, Faculty for Biological Sciences, Martin-Luther-University Halle-Wittenberg, 06120 Halle Saale, Germany.
Spinka
Michael
M
Tittmann
Kai
K
Schütz
Anja
A
Golbik
Ralph
R
Mrestani-Klaus
Carmen
C
Hübner
Gerhard
G
König
Stephan
S
D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide) / Q000235:genetics / Q000378:metabolism*; D000494:Allosteric Regulation / Q000502:physiology; D000596:Amino Acids / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation / Q000502:physiology; D007651:Keto Acids / Q000378:metabolism; D007700:Kinetics; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D013835:Thiamine Pyrophosphate / Q000378:metabolism*
D000596:Amino Acids; D001426:Bacterial Proteins; D007651:Keto Acids; D042942:3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide); D013835:Thiamine Pyrophosphate