Glycogen branching enzyme
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| 1,4-alpha-glucan branching enzyme
| |
| Identifiers | |
| Symbol | GBE1 |
| Entrez | 2632 |
| HUGO | 4180 |
| 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.
This enzyme belongs to the family of transferases, specifically those glycosyltransferases that transfer hexoses (hexosyltransferases). The systematic name of this enzyme class is 1,4-alpha-D-glucan:1,4-alpha-D-glucan 6-alpha-D-(1,4-alpha-D-glucano)-transferase. Other names in common use include branching enzyme, amylo-(1,4→1,6)-transglycosylase, Q-enzyme, alpha-glucan-branching glycosyltransferase, amylose isomerase, enzymatic branching factor, branching glycosyltransferase, enzyme Q, glucosan transglycosylase, 1,4-alpha-glucan branching enzyme, plant branching enzyme, alpha-1,4-glucan:alpha-1,4-glucan-6-glycosyltransferase, and starch branching enzyme. This enzyme participates in starch and sucrose metabolism.
Pathology
A defect in this enzyme can lead to disease; see glycogen storage disease type IV and glycogen branching enzyme deficiency.
Structural studies
As of late 2007, only one structure has been solved for this class of enzymes, with the PDB accession code 1M7X.
References
- IUBMB entry for 2.4.1.18
- BRENDA references for 2.4.1.18 (Recommended.)
- PubMed references for 2.4.1.18
- PubMed Central references for 2.4.1.18
- Google Scholar references for 2.4.1.18
- Barker SA, Bourne E and Peat S (Lond.). "The enzymic synthesis and degradation of starch. Part IV. The purification and storage of the Q-enzyme of the potato". J. Chem. Soc.: 1705–1711.
- Baum H and Gilbert GA (1953). "A simple method for the preparation of crystalline potato phosphorylase and Q-enzyme". Nature 171: 983–984.
- Hehre EJ (1951). "Enzymic synthesis of polysaccharides: a biological type of polymerization". Adv. Enzymol. Relat. Subj. Biochem. 11: 297–337.
- Handelsman DJ (2006). "Follicle-stimulating hormone increases primordial follicle reserve in mature female hypogonadal mice". J. Endocrinol. 188: 549–57. PMID 16522734.
External links
- The CAS registry number for this enzyme class is 9001-97-2.
Gene Ontology (GO) codes
| This transferase article is a stub. You can help WikiDoc by expanding it. |
Metabolism: carbohydrate metabolism - glycogenesis and glycogenolysis enzymes | |
|---|---|
| Glycogenesis | Phosphoglucomutase - UDP-glucose pyrophosphorylase - Glycogen synthase (Glycogen branching enzyme) |
| Glycogenolysis | Glycogen phosphorylase (Debranching enzyme) - Phosphoglucomutase - Glycogenin Maltase |
| Regulation | Phosphorylase kinase - Phosphoprotein phosphatase |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
