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Biochemistry. 2013 Apr 16;52(15):2505-7. doi: 10.1021/bi301591e. Epub 2013 Apr 1.

Alternating sites reactivity is a common feature of thiamin diphosphate-dependent enzymes as evidenced by isothermal titration calorimetry studies of substrate binding.

Author information

1
Göttingen Center for Molecular Biosciences, Georg-August-University Göttingen, Ernst-Caspari-Haus, Justus-von-Liebig-Weg 11,37077 Göttingen, Germany.

Abstract

Thiamin diphosphate (ThDP)-dependent enzymes play vital roles in cellular metabolism in all kingdoms of life. In previous kinetic and structural studies, a communication between the active centers in terms of a negative cooperativity had been suggested for some but not all ThDP enzymes, which typically operate as functional dimers. To further underline this hypothesis and to test its universality, we investigated the binding of substrate analogue methyl acetylphosphonate (MAP) to three different ThDP-dependent enzymes acting on substrate pyruvate, namely, the Escherichia coli E1 component of the pyruvate dehydrogenase complex, E. coli acetohydroxyacid synthase isoenzyme I, and the Lactobacillus plantarum pyruvate oxidase using isothermal titration calorimetry. The results unambiguously show for all three enzymes studied that only one active center of the functional dimers accomplishes covalent binding of the substrate analogue, supporting the proposed alternating sites reactivity as a common feature of all ThDP enzymes and resolving the recent controversy in the field.

PMID:
23544868
DOI:
10.1021/bi301591e
[Indexed for MEDLINE]

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