Catalytic subunit of the phosphorylase b kinase (PHK), which mediates the neural and hormonal regulation of glycogen breakdown (glycogenolysis) by phosphorylating and thereby activating glycogen phosphorylase. May regulate glycogeneolysis in the testis. In vitro, phosphorylates PYGM (PubMed:35549678). {ECO:0000250|UniProtKB:P31325, ECO:0000269|PubMed:10487978, ECO:0000269|PubMed:35549678}. This is the function of ENSG00000156873 (PHKG2, phosphorylase kinase catalytic subunit gamma 2).