ISOLATION OF CDNA-ENCODING THE HUMAN LIVER PHOSPHORYLASE-KINASE ALPHA-SUBUNIT (PHKA2) AND IDENTIFICATION OF A MISSENSE MUTATION OF THE PHKA2 GENE IN A FAMILY WITH LIVER PHOSPHORYLASE-KINASE DEFICIENCY

X-linked liver glycogenosis (XLG) due to liver phosphorylase kinase (P HK) deficiency is the most frequent liver glycogen storage disease. Th e affected patients present in early childhood with hepatomegaly and g rowth retardation. We isolated and determined the structure of human l iver alpha subunit of PHK (PHKA2) cDNA. The 3705 base pair open readin g frame encodes a polypeptide of 1235 amino acid residues, and the ded uced amino acid sequence shows 93 and 68% homology to that of rabbit l iver alpha subunit of PHK and human muscle alpha subunit of PHK, respe ctively. We identified a missense mutation, a valine substitution for glycine at amino acid 193, in the PHKA2 gene of a family with XLG.