Phosphorylase isoenzymes of human brain

The isoenzyme pattern of phosphorylase in human brain was studied by polyacrylamide slab gel electrophoresis and activity was revealed by iodine stain and by autoradiography: A major fast-migrating band was similar to isoenzyme I of the heart; an intermediate band migrated like the hybrid cardiac isoenzyme II; and a slow-migrating band, best revealed by autoradiography, migrated like the “muscle” isoenzyme III. The radioactivity in bands II and III accounted for 42% of total activity in the heart and 37% in the brain. Antibodies against mature muscle phosphorylase inhibited 41% of enzyme activity in heart extracts and 25% in brain extracts. These studies show that the “muscle” isoenzyme is a component of brain phosphorylase and suggest that partial phosphorylase deficiency occurs in the brain of patients with McArdle disease.