Glycogen branching enzyme 3602064 215507415 2008-05-28T14:39:16Z DOI bot 6652755 Citation maintenance. You can [[WP:DOI|use this bot]] yourself! Please [[User:DOI_bot/bugs|report any bugs]]. {{protein |Name=1,4-alpha-glucan branching enzyme |caption= |image= |width= |HGNCid=4180 |Symbol=GBE1 |AltSymbols= |EntrezGene=2632 |OMIM=607839 |RefSeq=NM_000158 |UniProt=Q04446 |PDB= |ECnumber=2.4.1.18 |Chromosome=3 |Arm=p |Band=12 |LocusSupplementaryData= }} 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 [[Catalysis|catalyzed]] by the enzyme [[glycogen synthase]]. [[Image:Glycogen.png|thumb|center|450px|Glycogen structure]] 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 [[transferase]]s, specifically those glycosyltransferases that transfer [[hexose]]s ([[hexosyltransferase]]s). 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 [[tertiary structure|structure]] has been solved for this class of enzymes, with the [[Protein Data Bank|PDB]] accession code {{PDB link|1M7X}}. ==References== {{reflist|1}} {{Enzyme references|EC_number=2.4.1.18|IUBMB_EC_number=2/4/1/18}} * {{cite journal | author = Barker SA, Bourne E and Peat S | date = Lond. | title = The enzymic synthesis and degradation of starch. Part IV. The purification and storage of the Q-enzyme of the potato | journal = J. Chem. | volume = Soc. | pages = 1705–1711 }} * {{cite journal | author = Baum H and Gilbert GA | date = 1953 | title = A simple method for the preparation of crystalline potato phosphorylase and Q-enzyme | journal = Nature | volume = 171 | pages = 983–984 | doi = 10.1038/171983a0 }} * {{cite journal | author = Hehre EJ | date = 1951 | title = Enzymic synthesis of polysaccharides: a biological type of polymerization | journal = Adv. Enzymol. Relat. Subj. Biochem. | volume = 11 | pages = 297–337 | doi = 10.1002/9780470122563.ch6 }} * {{cite journal | author = Handelsman DJ | date = 2006 | title = Follicle-stimulating hormone increases primordial follicle reserve in mature female hypogonadal mice | journal = J. Endocrinol. | volume = 188 | pages = 549–57 | pmid = 16522734 | doi = 10.1677/joe.1.06614 }} ==External links== ::''The [[CAS registry number]] for this enzyme class is {{CAS registry|9001-97-2}}.'' {{Enzyme links|EC_number=2.4.1.18|IUBMB_EC_number=2/4/1/18}} ===Gene Ontology (GO) codes=== {{GO code links | GO_code=0003844 | name=glycogen branching enzyme}} {{enzyme-stub}} [[Category:EC 2.4.1]] [[Category:Enzymes of known structure]] [[Category:Enzymes]] [[Category:Metabolism]] [[Category:Transferases]] {{transferase-stub}} {{Glycosyltransferases}} {{Glycogenesis and glycogenolysis}}