Describe the regulation of pyruvate dehydrogenase through covalent modification.
PDH exists in 2 forms : Inactive, phosphorylated and Active, dephosphorylated. The active form of PDH is phosphorylated by a protein kinase with the help of ATP and Mg++ to the inactive form of PDH. Acetyl CoA and NADH are activators for this action and CoA, NAD+, and pyruvate are inhibitors. The inactive form of PDH is dephosphorylated by phosphoprotein phosphatase to the active form in the presence of increased Ca++ ion concentration.