Purification and characterization of glycogen phosphorylase b from fat body of the silkworm, Bombyx mori

Abstract

1. 1. Glycogen phosphorylase b from silkworm pupal fat body has been purified to homogeneity as judged by native and SDS-gel electrophoreses. 2. 2. The enzyme is a monomeric protein having a mol. wt of approx. 92,000. 3. 3. The enzyme has an absolute requirement for AMP. The K m for AMP is in a range from 0.4 to 0.6 mM and for the maximum activity 2 mM is required. 4. 4. Phosphorylase b activity measured as a function of P i concentration shows positive cooperativity at any level of AMP. When measured as a function of glycogen concentration, however, the enzyme follows normal Michaelis-Menten kinetics.