PHKA2

Phosphorylase kinase is a polymer of 16 subunits, four each of alpha, beta, gamma and delta. The alpha subunit includes the skeletal muscle and hepatic isoforms, and the hepatic isoform is encoded by this gene. The beta subunit is the same in both the muscle and hepatic isoforms, and encoded by one gene. The gamma subunit also includes the skeletal muscle and hepatic isoforms, which are encoded by two different genes. The delta subunit is a calmodulin and can be encoded by three different genes. The gamma subunits contain the active site of the enzyme, whereas the alpha and beta subunits have regulatory functions controlled by phosphorylation. The delta subunit mediates the dependence of the enzyme on calcium concentration. Mutations in this gene cause glycogen storage disease type 9A, also known as X-linked liver glycogenosis. Alternatively spliced transcript variants have been reported, but the full-length nature of these variants has not been determined.

Full Name

phosphorylase kinase, alpha 2 (liver)

Function

Phosphorylase b kinase catalyzes the phosphorylation of serine in certain substrates, including troponin I. The alpha chain may bind calmodulin.

Biological Process

Carbohydrate metabolic processManual Assertion Based On ExperimentTAS:ProtInc
Cellular protein modification processManual Assertion Based On ExperimentTAS:ProtInc
Generation of precursor metabolites and energyManual Assertion Based On ExperimentTAS:ProtInc
Glycogen metabolic processIEA:UniProtKB-UniPathway

Cellular Location

Cell membrane

Involvement in disease

Glycogen storage disease 9A (GSD9A):
A metabolic disorder resulting in a mild liver glycogenosis with clinical symptoms that include hepatomegaly, growth retardation, muscle weakness, elevation of glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase, hypercholesterolemia, hypertriglyceridemia, and fasting hyperketosis. Two subtypes are known: type 1 or classic type with no phosphorylase kinase activity in liver or erythrocytes, and type 2 or variant type with no phosphorylase kinase activity in liver, but normal activity in erythrocytes. Unlike other glycogenosis diseases, glycogen storage disease type 9A is generally a benign condition. Patients improve with age and are often asymptomatic as adults. Accurate diagnosis is therefore also of prognostic interest.

PTM

Although the final Cys may be farnesylated, the terminal tripeptide is probably not removed, and the C-terminus is not methylated.