Figure 2. Inhibitory action of AcPH, AcPMe and AcPMe2 on isolated PDHC.

The reaction was started with 2 mM pyruvate after PDHC from rat heart had been preincubated at 37°C in 50 mM MOPS buffer (pH 7.6) containing 1 mM MgCl₂, 1 mM CaCl₂, 1 mM ThDP, 0.05 mM CoA, 2.5 mM NAD⁺, 1 mM DTT and indicated inhibitor concentrations. A. Concentration dependences of PDHC activity on the indicated inhibitors after 1 min preincubation. Non-linear regression to a hyperbolic function $(y=y_0+\frac{ab}{b+x})$ was made using SigmaPlot 12.0. B. Time-dependent inhibition of the overall PDHC activity by AcPH. PDHC was preincubated as described above with 0.15 μM AcPH, followed by the reaction start with 2 mM pyruvate at the indicated times. Velocities were measured from the linear part of the product accumulation curves during 0.5–3.5 min of the reaction. Inhibition is presented as % of control activity in the absence of AcPH. Non-linear regression to an exponential decay function (y=y₀e^−kx) was made using SigmaPlot 12.0.