[Glycogen phosphorylase isozymes from chicken tissues and changes in the isozyme ratio during ontogenesis]

The isolation of isozymes Ib, IIIb and Lb of glycogen phosphorylase (EC 2.4.1.1) from chicken tissue is described. Isozymes Ib and IIIb have the same value of Km(G-1-P), i.e. 6.2 mM at 2 mM AMP but differ in A0.5(AMP). Isozyme Lb is characterized by S0.5(G-1-P) of 15 mM at 2 mM AMP and A0.5(AMP) of 600 muM at 20 mM G-1-P; for isozyme La these parameters are 3.7 mM and 20 muM, respectively. All the three isozymes reveal distinct immunochemical differences. In embryonic skeletal muscle the enzyme is represented by isozymes L and III up to the 15th way of embryogenesis; after the 17th day--only by isozyme III. In chicken liver the enzyme is represented only by isozyme L beginning with the 9th day of embryogenesis. At the beginning of tissue differentiation stage (4th day of embryogenesis) fetal tissues were found to contain isozymes L and IL.