Effects of conditions favoring enzyme phosphorylation and dephosphorylation on the activity of the alpha-keto acid dehydrogenases, with particular reference to the branched-chain alpha-keto acid dehydrogenase activities.

These studies have shown that in the crude system of rat liver mitochondria the branched-chain α-keto acid dehydrogenase activities are activated at high (10.0mM) Mg⁺⁺ concentrations favoring dephosphorylation, and are inactive at low (1.0mM) Mg⁺⁺ concentrations favoring phosphorylation. In this crude system, α-Ketoglutarate dehydrogenase activity was also regulated in this manner. In general, the optimum Mg⁺⁺ and ATP levels for activation were 10mM and 1.0mM respectively.