Glycogen branching enzyme
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1,4-alpha-glucan branching enzyme
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| Identifiers | |
| Symbol | GBE1 |
| HUGO | 4180 |
| Entrez | 2632 |
| OMIM | 607839 |
| RefSeq | NM_000158 |
| UniProt | Q04446 |
| Other data | |
| EC number | 2.4.1.18 |
| Locus | Chr. 3 p12 |
A glycogen branching enzyme is an enzyme taking part in the synthesis of glycogen by adding branches to the glycogen molecule. Glycogen is a branching polymer of large numbers of glucose units linked together. The structure is based on chains of glucose units with linkages between carbon atoms 1 and 4 of each pair of units (alpha 1, 4 linkages). These linkages are catalyzed by the enzyme glycogen synthase.
Every 10 to 14 glucose units a side branch with an additional chain of glucose units occurs. The side chain attaches at carbon atom 6 of a glucose unit, and the linkage is termed an alpha-1,6 glycosidic bond. To form this connection a separate enzyme known as a branching enzyme is used. A branching enzyme attaches a string of seven glucose units to the sixth carbon of a glucose unit, usually in an interior location of the glycogen molecule.
A defect in this enzyme can lead to disease; see glycogen storage disease type IV and glycogen branching enzyme deficiency.
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Hexosyltransferases: Glucosyltransferases (Glycogen branching enzyme, Glycogen synthase, Glycogen phosphorylase, Phosphorylase/Myophosphorylase) - Glucuronosyltransferase
Pentosyltransferases: Adenine phosphoribosyltransferase - Hypoxanthine-guanine phosphoribosyltransferase - ADP Ribose (Cholera toxin, Diphtheria toxin, Pertussis toxin, Poly ADP ribose polymerase)
