title: Glucoamylase-like domains in the alpha- and beta-subunits of phosphorylase kinase.
abstract: Phosphorylase kinase is a four-subunit enzyme involved in the regulation of glycogen breakdown. The traditional textbook view is that only the gamma subunit has enzymatic activity, whereas the other three subunits have a regulatory role. Evidence from homology searches and sequence alignments, however, shows that the alpha- and beta-subunits possess amino-terminal glucoamylase-like domains and suggests that they might possess a previously overlooked amylase activity. If true, this would have important implications for the understanding, diagnosis, and management of glycogen storage diseases. There is thus a clear need to test this hypothesis through enzymatic assays and structural studies.
authors.affiliation: Division of Immunity and Infection, University of Birmingham Medical School, Vincent Drive, Edgbaston, Birmingham B15 2TT, UK. m.pallen@bham.ac.uk
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Pallen
mesh_terms: D000595:Amino Acid Sequence; D004926:Escherichia coli; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010764:Phosphorylase Kinase / Q000737:chemistry* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D021122:Protein Subunits; D010764:Phosphorylase Kinase; D005087:Glucan 1,4-alpha-Glucosidase