The roles of intrinsic kinase and of kinase/activator protein in the enhanced phosphorylation of pyruvate dehydrogenase complex in starvation.

Extracts of heart mitochondria from fed and from 48 h starved rats subjected to gel filtration on Sephacryl S-300 gave 4 major protein peaks. Pyruvate dehydrogenase complex eluted in the void volume and was assayed for intrinsic pyruvate dehydrogenase kinase activity which was increased approximately 3-fold by 48 h starvation of the rat. A second fraction, containing peaks 2 and 3 which overlapped, enhanced the activity of the intrinsic kinase and corresponds to kinase/activator protein described previously. Its activity was increased 1.5-fold by starvation.