PHKA2
Chr XXLRphosphorylase kinase regulatory subunit alpha 2
Also known as: GSD9A, PHK, PYK, PYKL, XLG, XLG2
The PHKA2 gene encodes the hepatic alpha subunit of phosphorylase kinase, a regulatory enzyme in glycogen metabolism where the alpha subunit controls enzyme activity through phosphorylation while the gamma subunit contains the catalytic site. Mutations cause glycogen storage disease types IXa1 and IXa2 (X-linked liver glycogenosis) through loss of phosphorylase kinase regulation, leading to impaired glycogen breakdown in the liver. This follows X-linked recessive inheritance, primarily affecting males.
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
More LoF-intolerant than ~75% of genes
Mild missense constraint
ClinVar Variant Classifications
100 submitted variants in ClinVar
Classification Summary
Curated Variants Distribution
Classified variants from ClinVar · 5 ACMG categories
| Classification | LoF | Missense + Inframe | Non-coding | Synonymous | Total |
|---|---|---|---|---|---|
Pathogenic | 1 | 0 | 3 | 0 | 4 |
Likely Pathogenic | 3 | 2 | 0 | 0 | 5 |
VUS | 0 | 30 | 7 | 0 | 37 |
Likely Benign | 0 | 4 | 18 | 21 | 43 |
Benign | 0 | 0 | 2 | 2 | 4 |
| Total | 4 | 36 | 30 | 23 | 93 |
LoF = frameshift, stop gained/lost, canonical splice · Counts from ClinVar esearch · Updated hourly
View in ClinVar →Protein Context — Lollipop Plot
PHKA2 · protein map & ClinVar variants
Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.
3D Protein StructureAlphaFold
External Resources
Links to major genomics databases and tools
Clinical Trials
Active and recruiting trials from ClinicalTrials.gov
No active trials found for this gene.
Search ClinicalTrials.gov →External Resources
Links to major genomics databases and tools