Protein phosphatase interconversions

This report illustrates the complex enzymology of the multisubstrate protein phosphate that reverses most of the cyclic AMP-mediated protein phosphorylation reactions that regulate glycogen metabolism. The activity of the protein phosphatase is controlled in a dual way: it interconverts between an active and an inactive form, while the expression of its activity can furthermore be prevented by a heat-stable protein (inhibitor-1). The interconversion of the mutisubstrate protein phosphatase is made possible by the presence of a modulator protein, which constitutes the enzyme's regulatory subunit, and by the action of an activating protein, the kinase F_A, which is responsible for the transition of the enzyme's catalytic subunit into its active conformation.