Meyahealth
HomeGeneticsGenePHKB gene
Back to Gene
PHKB gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

PHKB gene

The PHKB gene provides instructions for creating the beta subunit of the phosphorylase b kinase enzyme, which is critical for glycogen breakdown in both the liver and muscles.

Normal Function

The PHKB gene provides instructions for making one piece, the beta subunit, of the phosphorylase b kinase enzyme. This enzyme is made up of 16 subunits, four each of the alpha, beta, gamma, and delta subunits. The beta subunit helps regulate the activity of phosphorylase b kinase. This enzyme is found in various tissues, although it is most abundant in the liver and muscles. The beta subunit produced from the PHKB gene is part of the enzyme found both in the liver and in muscle.

Phosphorylase b kinase plays an important role in providing energy for cells. The main source of cellular energy is a simple sugar called glucose. Glucose is stored in muscle and liver cells in a form called glycogen. Glycogen can be broken down rapidly when glucose is needed, for instance during exercise. Phosphorylase b kinase turns on (activates) another enzyme called glycogen phosphorylase b by converting it to the more active form, glycogen phosphorylase a. When active, this enzyme breaks down glycogen.

Health Conditions Related to Genetic Changes

Glycogen storage disease type IX

At least 21 mutations in the PHKB gene are known to cause a form of glycogen storage disease type IX (GSD IX) called GSD IXb. This form of the disorder affects the liver and the muscles. The liver problems caused by this disorder include:

  • An enlarged liver (hepatomegaly)
  • Slow growth
  • Periods of low blood glucose (hypoglycemia)

These features usually improve over time. The condition can also cause mild muscle weakness, although some affected individuals have no muscle problems.

Mutations in the PHKB gene reduce the activity of phosphorylase b kinase in liver and muscle cells. Reduction of this enzyme's function impairs glycogen breakdown. As a result, glycogen builds up in cells, and glucose is not available for energy. The inability to break down glycogen in the liver and reduced energy production in muscle cells lead to the features of GSD IXb.

Other Names for This Gene

  • KPBB_HUMAN
  • phosphorylase b kinase regulatory subunit beta
  • phosphorylase kinase beta subunit
  • phosphorylase kinase beta-subunit
  • phosphorylase kinase subunit beta
  • phosphorylase kinase, beta

Frequently Asked Questions

definitive diagnosis requires a DNA test that sequences the PHKB gene for known pathogenic variants. The test is usually done on a blood sample and can be ordered by a geneticist or a metabolic specialist. In some cases, a liver biopsy may be performed to assess glycogen content and enzyme activity, but the genetic test is the gold standard.
The disorder is inherited in an autosomal recessive pattern, meaning both parents must carry a faulty copy of the gene for a child to be affected. If both parents are carriers, there is a 25 % chance with each pregnancy that the child will inherit two defective copies and develop the disease. Genetic counseling can help families understand risks and discuss options such as prenatal testing or preimplantation genetic diagnosis.
Frequent, balanced meals that include complex carbohydrates and a bedtime snack with slow‑digesting carbs (like a small portion of whole‑grain cereal or a banana) can help maintain steady blood sugar. Some families also use uncooked cornstarch as a slow‑release carbohydrate overnight. A dietitian experienced with glycogen storage diseases can tailor a plan that keeps glucose levels stable while supporting growth.
Parents may notice a swollen abdomen from an enlarged liver, poor weight gain or growth delays, and episodes of low blood sugar that can cause shakiness, sweating, or fainting. If these symptoms appear, especially in a child who is not thriving, a pediatrician may order liver function tests and a blood glucose curve to look for hypoglycemia.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

Meyahealth

Ⓒ 2026. All rights reserved by MEYA

About UsTerms & PolicyFAQ