Hepatic phosphorylase b kinase deficiency with normal enzyme activity in leukocytes

Abstract

Glycogen phosphorylase b kinase (EC 2.7.1.38) is responsible for the activation, by phosphorylation, of phosphorylase b to phosphorylase a. Deficiency o f this enzyme complex in man (McKusick 30600) was first documented by Hug et a12 Three girls and two boys were found to be deficient in PBK activity in liver homogenate. These and subsequent patients having an autosomal recessive mode of inheritance of PBK deficiency, were found clinically tO have moderate hepatomegaly, variable muscle weakness, normal growth and development, and normal response to glucagon. 2 Another group of patients, all boys, were found to have varying hepatomegaly, fasting hypoglycemia, a reduced response to glucagon, and retarded growth and development with an X-linked pattern of inheritance2 Patients with the autosomal recessive form of PBK deficiency ~'iJave 20% to 30% of normal control PBK activity in erythrocytes, leukocytes, and liver. 2 Male patients with the X-linked form of the deficiency have almost no PBK activity in liver, approximately 20% in leukocytes, and normal activity in muscle. 2 We report a patient with reduced liver homogenate and erythrocyte lysate PBK activity with normal leukocyte and muscle homogenate enzyme activity.