Phosphorylase b kinase gamma catalytic chain, skeletal muscle/heart isoform

PHKG1 encodes the catalytic subunit of phosphorylase b kinase (PHK), a serine/threonine kinase that regulates glycogen breakdown by phosphorylating glycogen phosphorylase. The enzyme also phosphorylates substrates including tau protein (MAPT), growth-associated protein 43 (GAP43), and recoverin (NRGN/RC3) in vitro (UniProt: Q16816). This isoform is expressed in skeletal muscle and heart tissue and is involved in neural and hormonal regulation of glucose metabolism. No baseline disease associations are documented in UniProt for PHKG1.

In Alzheimer's Disease, PHKG1 is upregulated in post-mortem brain tissue from AD patients compared to age-matched controls (Chaparral AD proteomics). The mean log2 fold-change is 0.89 in a TMT-labeled mass spectrometry study of four subcellular fractions (P2, P3, S2, S3) from human post-mortem brain. The consistent upregulation across fractions suggests increased kinase availability in AD brain, which may influence tau phosphorylation or related neurodegenerative pathways, though functional consequences remain to be determined.