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• Author: Stefan Janecek
• Responsible Curator: Stefan Janecek

Substrate specificities

Glycoside hydrolase family 77 is the member of the α-amylase clan GH-H [1], together with GH13 and GH70 [2]. The family contains only one enzyme specificity - the amylomaltase (EC 2.4.1.25), that is known as disproportionating enzyme (D-enzyme) in plants [3] or 4-α-glucanotransferase in bacteria [4] and archaeons [5]. As of April 2010, it has more than 700 members [1] with more than 650 from Bacteria, ~10 from Archaea and a few tens from Eukarya (plants and green algae).

Amylomaltase catalyses the glucan-chain transfer from one α-1,4-glucan to another α-1,4-glucan (or to 4-hydroxyl group of glucose) or within a single linear glucan molecule to produce a cyclic α-1,4-glucan with degree of polymerization starting from 17 [3, 4, 5]. Cyclodextrin glucanotransferase, a member of the α-amylase family GH13, also produces cyclic α-1,4-glucans, but with a small degree of polymerization (6-8), called cyclodextrins [6].

Kinetics and Mechanism

Catalytic Residues

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Three-dimensional structures

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Family Firsts

First stereochemistry determination

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First catalytic nucleophile identification

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First general acid/base residue identification

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First 3-D structure

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References

1. Cantarel BL, Coutinho PM, Rancurel C, Bernard T, Lombard V, and Henrissat B. The Carbohydrate-Active EnZymes database (CAZy): an expert resource for Glycogenomics. Nucleic Acids Res 2009 Jan; 37(Database issue) D233-8. doi:10.1093/nar/gkn663 pmid:18838391. PubMed HubMed [Cantarel2009]
2. MacGregor EA, Janecek S, and Svensson B. Relationship of sequence and structure to specificity in the alpha-amylase family of enzymes. Biochim Biophys Acta 2001 Mar 9; 1546(1) 1-20. pmid:11257505. PubMed HubMed [MacGregor2001]
3. Takaha T, Yanase M, Okada S, and Smith SM. Disproportionating enzyme (4-alpha-glucanotransferase; EC 2.4.1.25) of potato. Purification, molecular cloning, and potential role in starch metabolism. J Biol Chem 1993 Jan 15; 268(2) 1391-6. pmid:7678257. PubMed HubMed [Takaha1993]
4. Terada Y, Fujii K, Takaha T, and Okada S. Thermus aquaticus ATCC 33923 amylomaltase gene cloning and expression and enzyme characterization: production of cycloamylose. Appl Environ Microbiol 1999 Mar; 65(3) 910-5. pmid:10049841. PubMed HubMed [Terada1999]
5. Kaper T, Talik B, Ettema TJ, Bos H, van der Maarel MJ, and Dijkhuizen L. Amylomaltase of Pyrobaculum aerophilum IM2 produces thermoreversible starch gels. Appl Environ Microbiol 2005 Sep; 71(9) 5098-106. doi:10.1128/AEM.71.9.5098-5106.2005 pmid:16151092. PubMed HubMed [Kaper2005]
6. Leemhuis H, Kelly RM, and Dijkhuizen L. Engineering of cyclodextrin glucanotransferases and the impact for biotechnological applications. Appl Microbiol Biotechnol 2010 Jan; 85(4) 823-35. doi:10.1007/s00253-009-2221-3 pmid:19763564. PubMed HubMed [Leemhuis2010]