Oxidative decarboxylation is observed in which step of aerobic respiration?

Pyruvate, which is formed by the glycolytic catabolism of carbohydrates in the cytosol, enters into mitochondrial matrix and undergoes oxidative decarboxylation by a complex set of reactions catalysed by pyruvic dehydrogenase. The reactions catalysed by pyruvic dehydrogenase requires the participation of several coenzymes, including NAD+ and Coenzyme A.

$\mathrm{Pyruvic} \mathrm{acid}+\mathrm{CoA}+{\mathrm{NAD}}^{+}\underset{\mathrm{Pyruvate} \mathrm{dehydrogenase}}{\overset{{\mathrm{Mg}}^2}{\to }}\mathrm{Acetyl} \mathrm{CoA}+{\mathrm{CO}}_2+\mathrm{NADH}+{\mathrm{H}}^{+}$