Type VI glycogenosis: Biochemical demonstration of liver phosphorylase deficiency

Abstract A boy with hepatomegaly had increased glycogen and low activity of liver phosphorylase. Muscle tissue was normal. Conversion of rabbit muscle phosphorylase b to phosphorylase a by his liver homogenate indicated its normal capacity for phosphorylase activation. The patient's hepatic homogenate failed to develop phosphorylase activity under conditions that in control homogenates revealed the presence of endogenous phosphorylase through its activation. The failure was not corrected by the addition of phosphorylase kinase to the patient's homogenate. The results indicate liver phosphorylase deficiency or type VI glycogenosis.