Glycogen debranching enzyme

amylo-1, 6-glucosidase, 4-alpha-glucanotransferase (glycogen debranching enzyme, glycogen storage disease type III)
Identifiers
Symbol	AGL
Entrez	178
HUGO	321
OMIM	232400
RefSeq	NM_000028
UniProt	P35573
Other data
EC number	2.4.1.25
Locus	Chr. 1 p21

A debranching enzyme is a molecule that helps facilitate the breakdown of glycogen.

Function

Debranching enzymes work by first transferring three glucose subunits of glycogen from one parallel chain to another. This shortens one linear branch while lengthening another. Afterwards, the donator branch will contain only one glucose residue with alpha-1,6 linkage. This remaining residue is in turn cut by the alpha-1,6 glucosidase activity of the debranching enzyme, and attached to the remaining linear branch. This two step process is the general mechanism by which the debranching enzyme "straightens out" glycogen into an unbranched glucose polymer.

These enzymes are important in glycogenolysis because the cutting enzyme, glycogen phosphorylase, cannot cut a non-linear (or branched) glycogen chain.

Enzyme classification

The two debranching enzymes are:

• 4-α-D-glucanotransferase (EC 2.4.1.25) - glucosyltransferase
• amylo-α-1,6-glucosidase (EC 3.2.1.33) - glucosidase

Pathology

Deficiency in either of these enzymes will result in Glycogen storage disease type III.

External links

• MeSH Glycogen+debranching+enzyme