Reaction: linear α-glucan = (n-1) 1,5-anhydro-D-fructose + D-glucose
For diagram of reaction click here.
Other name(s): α-(1→4)-glucan 1,5-anhydro-D-fructose eliminase; α-1,4-glucan exo-lyase; α-1,4-glucan lyase; GLase
Systematic name: (1→4)-α-D-glucan exo-4-lyase (1,5-anhydro-D-fructose-forming)
Comments: The enzyme catalyses the sequential degradation of (1→4)-α-D-glucans from the non-reducing end with the release of 1,5-anhydro-D-fructose. Thus, for an α-glucan containing n (1→4)-linked glucose units, the final products are 1 glucose plus (n-1) 1,5-anhydro-D-fructose. Maltose, maltosaccharides and amylose are all completely degraded. It does not degrade (1→6)-α-glucosidic bonds and thus the degradation of a branched glucan, such as amylopectin or glycogen, will result in the formation of 1,5-anhydro-D-fructose plus a limit dextrin. The other enzymes involved in this pathway are EC 4.2.1.110 (aldos-2-ulose dehydratase), EC 4.2.1.111 (1,5-anhydro-D-fructose dehydratase) and EC 5.3.2.7 (ascopyrone tautomerase).
Links to other databases: BRENDA, EAWAG-BBD, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 148710-18-3
References:
1. Yu, S., Kenne, L., Pedersén, M. α-1,4-Glucan lyase, a new class of starch/glycogen degrading enzyme. I. Efficient purification and characterization from red seaweeds. Biochim. Biophys. Acta 1156 (1993) 313-320. [PMID: 8461323]
2. Yu, S., Pedersén, M. α-1,4-Glucan lyase, a new class of starch/glycogen degrading enzyme. II. Subcellular localization and partial amino-acid sequence. Planta 191 (1993) 137-142.
3. Yu, S., Ahmad, T., Kenne, L. and Pedersén, M. α-1,4-Glucan lyase, a new class of starch/glycogen degrading enzyme. III. Substrate specificity, mode of action, and cleavage mechanism. Biochim. Biophys. Acta 1244 (1995) 1-9. [PMID: 7766642]
4. Yu, S., Christensen, T.M., Kragh, K.M., Bojsen, K. and Marcussen, J. Efficient purification, characterization and partial amino acid sequencing of two α-1,4-glucan lyases from fungi. Biochim. Biophys. Acta 1339 (1997) 311-320. [PMID: 9187252]
5. Yu, S., Bojsen, K., Svensson, B. and Marcussen, J. α-1,4-glucan lyases producing 1,5-anhydro-D-fructose from starch and glycogen have sequence similarity to α-glucosidases. Biochim. Biophys. Acta 1433 (1999) 1-15. [PMID: 10446355]
6. Lee, S.S., Yu, S. and Withers, S.G. α-1,4-Glucan lyase performs a trans-elimination via a nucleophilic displacement followed by a syn-elimination. J. Am. Chem. Soc. 124 (2002) 4948-4949. [PMID: 11982345]
7. Lee, S.S., Yu, S. and Withers, S.G. Detailed dissection of a new mechanism for glycoside cleavage: α-1,4-glucan lyase. Biochemistry 42 (2003) 13081-13090. [PMID: 14596624]