Interconvertible forms of glycogen phosphorylase in Neurospora crassa

Glycogen phosphorylase in extracts of N. crassa mycelia has two interconvertible forms: one active (a form) and the other inactive (b form) in the absence of 5'-AMP. The conversion of the b to the a form requires ATP-Mg(2+) and proceeds at higher rate in the presence of 3',5'-cyclic AMP.