The purified aurochs (Bison bonasus, European bison) heart pyruvate dehydrogenase complex (PDC) has a set of subunits typical of mammalian PDC. PDC from aurochs heart contains firmly bound tiamine pyrophosphate in the amount providing over 50% of the maximal activity of the complex. The apparent value for activation energy of PDC is 60 kJ/mol. The Michaelis constant values for aurochs heart PDC are 22.4 +/- 1.0, 3.3 +/- 0.1 and 24.4 +/- 3.6 microM for pyruvate, CoA and NAD, accordingly. Acetyl-CoA is a competitive inhibitor with respect to CoA (Ki = 14.2 +/- 0.4 microM), whereas NADH gives the same inhibition with respect to NAD (Ki = 46.9 +/- 10.0 microM). The Km for CoA and NAD of the aurochs heart PDC are lower than that of domestic animals PDC.
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