Glycogen branching enzyme 1 (GBE1)

Glycogen branching enzyme 1 (GBE1) is a glycosyltransferase enzyme responsible for introducing α-1,6-linked branches into the glycogen molecule during glycogen biosynthesis. This branching is critical for creating the compact, highly branched structure of glycogen, which increases its solubility and allows for rapid mobilization of glucose when needed. GBE1’s action helps store energy efficiently and regulate osmotic pressure within cells; it is most highly expressed in liver and muscle. Mutations in the GBE1 gene cause glycogen storage disease type IV (Andersen's disease), characterized by abnormal glycogen with reduced branching, leading to liver dysfunction, neuromuscular symptoms, and, in some cases, adult polyglucosan body disease (APBD) with neurological features. There are currently no approved drugs that target GBE1, but enzyme stabilization and gene therapies are areas of research interest.

Other names

1,4-alpha-glucan branching enzyme 1Glycogen-branching enzymeBrancher enzymeAmylo-(1,4→1,6)-transglycosylaseQ-enzymeAlpha-glucan-branching glycosyltransferaseAmylose isomeraseEnzymatic branching factorBranching glycosyltransferaseEnzyme QGlucosan transglycosylasePlant branching enzymeAlpha-1,4-glucan:alpha-1,4-glucan-6-glycosyltransferaseStarch branching enzyme

Drugs or compounds (e.g., small molecule chaperones or stabilizers, such as experimental peptides) may act by stabilizing mutant GBE1 protein to restore enzymatic function in cases of deficiency. Acarbose inhibits the enzyme by binding to a non-catalytic site, but is not a clinically used therapy for GBE1 deficiency