Reaction: Hydrolysis of (1→6)-α-D-glucosidic linkages to branches with degrees of polymerization of three or four glucose residues in limit dextrin.
Other name(s): glgX (gene name); glycogen debranching enzyme (ambiguous)
Systematic name: glycogen phosphorylase-limit dextrin maltotetraose-hydrolase
Comments: This bacterial enzyme catalyses a reaction similar to EC 220.127.116.11, amylo-α-1,6-glucosidase (one of the activities of the eukaryotic glycogen debranching enzyme). However, while EC 18.104.22.168 removes single glucose residues linked by 1,6-α-linkage, and thus requires the additional activity of 4-α-glucanotransferase (EC 22.214.171.124) to act on limit dextrins formed by glycogen phosphorylase (EC 126.96.36.199), this enzyme removes maltotriose and maltotetraose chains that are attached by 1,6-α-linkage to the limit dextrin main chain, generating a debranched limit dextrin without a need for another enzyme.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
1. Jeanningros, R., Creuzet-Sigal, N., Frixon, C. and Cattaneo, J. Purification and properties of a debranching enzyme from Escherichia coli, Biochim. Biophys. Acta 438 (1976) 186-199. [PMID: 779849]
2. Dauvillee, D., Kinderf, I.S., Li, Z., Kosar-Hashemi, B., Samuel, M.S., Rampling, L., Ball, S. and Morell, M.K. Role of the Escherichia coli glgX gene in glycogen metabolism. J. Bacteriol. 187 (2005) 1465-1473. [PMID: 15687211]
3. Song, H.N., Jung, T.Y., Park, J.T., Park, B.C., Myung, P.K., Boos, W., Woo, E.J. and Park, K.H. Structural rationale for the short branched substrate specificity of the glycogen debranching enzyme GlgX. Proteins 78 (2010) 1847-1855. [PMID: 20187119]