Studies on phosphorylase isozymes in lower vertebrates: Purification and properties of lamprey phosphorylase

Abstract

Skeletal muscle phosphorylase b has been purified from lamprey, Entosphenus japonicus, to a state of homogeneity as judged by the criterion of sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The enzyme was completely dependent on AMP for activity and converted into the a form by rabbit muscle phosphorylase kinase in the presence of ATP and Mg 2+. The subunit molecular weight determined by SDS-gel electrophoresis was 94,000 ± 1,600 (SE). The enzyme activity was stimulated by Na 2SO 4, but was not affected by mercaptoethanol. The K m values of the a form for glucose 1-phosphate and glycogen were 3.5 m m and 0.13%, respectively, and those of the b form for glucose 1-phosphate, glycogen, and AMP were 15 m m, 0.4%, and 0.1 m m, respectively. These values were smaller than those reported with lobster phosphorylase and greater than those reported with mammalian skeletal muscle phosphorylases. Electrophoretic and immunological studies have indicated that lamprey phosphorylase b exists as a single molecular form in skeletal muscle, heart, brain, and kidney. Rabbit antibody against lamprey phosphorylase cross-reacted with phosphorylases from skate and shark livers more intensely than with those from skeletal muscles.