PHKB

Chr 16AR

phosphorylase kinase regulatory subunit beta

NCBI Gene: 5257 ENSG00000102893 UniProt: Q93100

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, encoded by two different genes. The beta subunit is the same in both the muscle and hepatic isoforms, encoded by this gene, which is a member of the phosphorylase b kinase regulatory subunit family. The gamma subunit also includes the skeletal muscle and hepatic isoforms, 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 9B, also known as phosphorylase kinase deficiency of liver and muscle. Alternatively spliced transcript variants encoding different isoforms have been identified in this gene. Two pseudogenes have been found on chromosomes 14 and 20, respectively.[provided by RefSeq, Feb 2010]

Primary Disease Associations & Inheritance

Phosphorylase kinase deficiency of liver and muscle, autosomal recessiveMIM #261750

UniProtGlycogen storage disease 9B

Active trials

Pathogenic / LP

ClinVar variants

Pubs (1 yr)

0.3

Missense Z

0.84

LOEUF

Clinical Summary— PHKB

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Gene-Disease Validity (ClinGen)

glycogen storage disease IXb · ARDefinitive

Definitive — sufficient evidence for diagnostic panels

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Population Constraint (gnomAD)

Low constraint (pLI 0.00) — loss-of-function variants are relatively tolerated in the population.

Population Genetics & Constraint

gnomAD v4 — loss-of-function & missense intolerance

gnomAD

Tolerant — LoF & missense variants common in population

LoF Constraint?LOEUF (Loss-of-function Observed/Expected Upper bound Fraction) is the upper bound of the 90% CI for LoF OE — the preferred gnomAD v4 metric. Lower = more intolerant to LoF. LOEUF < 0.35 = highly constrained.

0.84LOEUF

pLI 0.000

Z-score 2.66

OE 0.65 (0.51–0.84)

Tolerant

Typical tolerance to LoF variation

Missense Constraint?Missense Z-score: standard deviations fewer missense variants observed vs. expected. Z > 3.09 (p < 0.001) = gene does not tolerate missense variation. OE missense < 0.6 is also considered constrained.

0.30Z-score

OE missense 0.97 (0.90–1.03)

568 obs / 588.4 exp

Tolerant

Mild missense constraint

Observed / Expected Ratios?Shaded band = 90% confidence interval. Vertical tick = point estimate. Grey threshold line = gnomAD constraint cutoff for that variant class.

LoF OE?Ratio of observed to expected LoF variants. Upper CI bound (LOEUF) ≤ 0.35 = strong LoF constraint signal.0.65 (0.51–0.84)

0≤0.351.4

Missense OE?Ratio of observed to expected missense variants. OE ≤ 0.6 = fewer missense variants than expected by chance.0.97 (0.90–1.03)

0≤0.61.4

Synonymous OE?Control metric — synonymous variants are largely neutral and expected near OE = 1.0. Significant deviation may indicate annotation issues.0.94

0≤1.21.6

LoF obs/exp: 44 / 67.6Missense obs/exp: 568 / 588.4Syn Z: 0.74

0.6065th %ile

GOF

0.6639th %ile

LOF

0.3746th %ile

The highest-scoring mechanism for this gene is gain-of-function.

GOFprediction above median

Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.

Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.