Carbohydrate-active enzymes

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• Authors: ^^^Stephen Withers^^^, ^^^Spencer Williams^^^, and ^^^Harry Brumer^^^
• Responsible Curator: ^^^Spencer Williams^^^

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Individual monosaccharide units have the potential to be joined together to form oligo- and polysaccharides, with the glycosidic linkage occurring between the anomeric position of one sugar with the hydroxyl group of another [1]. Owing to the many hydroxy groups on each sugar, the potential for two possible anomeric configurations, and the possibility of different ring sizes (pyranose and furanose are the most common), there is a combinatorially-large number of structures possible [2]. Further, carbohydrates can be linked to other, non-carbohydrate molecules to generate a wide range of glycoconjugates [3]. Reflecting this structural diversity, there is a large diversity of enzymes involved in the biosynthesis, modification, binding and catabolism of carbohydrates.

The Carbohydrate Active EnZyme ("CAZy") classification

The Carbohydrate Active EnZyme (CAZy) classification is a sequence-based classification of enzymes that are active on carbohydrate structures, which originated with the seminal classification of glycoside hydrolases by ^^^Bernard Henrissat^^^ ([4, 5, 6]; see [7] for a lucid historical review). The creation of a family requires at least one biochemically-characterized member, and is based on the concept that sequence defines protein structure, and protein structure defines function. Generally, but not exclusively, functional properties often extend to other members of the family, and provides a framework upon which to base testable hypotheses of enzyme structure and function [8]. Since its inception, the CAZy classification and associated database has undergone continually active curation, including the addition of new enzyme and associated module classes [9, 10]. Hence, the CAZy classification presently comprises the following modules:

• Glycoside Hydrolase Families [4, 5, 6]
• Glycosyltransferase Families [11, 12, 13]
• Polysaccharide Lyase Families [14]
• Auxiliary Activity Families [15]
• Carbohydrate Binding Module Families (these are technically not catalytically active on carbohydrate structures, but owing to their association with catalytic modules, are included within the classsification scheme).

Further information on the composition of the families and mechanistic details can be obtained via these pages and the corresponding Lexicon entries.

References

1. Robert V. Stick and Spencer J. Williams. (2009) Carbohydrates. Elsevier Science.
2. Laine RA (1994). A calculation of all possible oligosaccharide isomers both branched and linear yields 1.05 x 10(12) structures for a reducing hexasaccharide: the Isomer Barrier to development of single-method saccharide sequencing or synthesis systems. Glycobiology. 1994;4(6):759-67. DOI:10.1093/glycob/4.6.759 |
3. Maureen E. Taylor and Kurt Drickamer. (2011-04-21) Introduction to Glycobiology. Oxford University Press.
4. Henrissat B (1991). A classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem J. 1991;280 ( Pt 2)(Pt 2):309-16. DOI:10.1042/bj2800309 |
5. Henrissat B and Bairoch A. (1993). New families in the classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem J. 1993;293 ( Pt 3)(Pt 3):781-8. DOI:10.1042/bj2930781 |
6. Henrissat B and Bairoch A. (1996). Updating the sequence-based classification of glycosyl hydrolases. Biochem J. 1996;316 ( Pt 2)(Pt 2):695-6. DOI:10.1042/bj3160695 |

7. Davies, G.J. and Sinnott, M.L. (2008) Sorting the diverse: the sequence-based classifications of carbohydrate-active enzymes. Biochem. J. (A BJ Classics review, online only). DOI: 10.1042/BJ20080382

8. Davies G and Henrissat B. (1995). Structures and mechanisms of glycosyl hydrolases. Structure. 1995;3(9):853-9. DOI:10.1016/S0969-2126(01)00220-9 |
9. Cantarel BL, Coutinho PM, Rancurel C, Bernard T, Lombard V, and Henrissat B. (2009). The Carbohydrate-Active EnZymes database (CAZy): an expert resource for Glycogenomics. Nucleic Acids Res. 2009;37(Database issue):D233-8. DOI:10.1093/nar/gkn663 |
10. Lombard V, Golaconda Ramulu H, Drula E, Coutinho PM, and Henrissat B. (2014). The carbohydrate-active enzymes database (CAZy) in 2013. Nucleic Acids Res. 2014;42(Database issue):D490-5. DOI:10.1093/nar/gkt1178 |
11. Campbell JA, Davies GJ, Bulone V, and Henrissat B. (1997). A classification of nucleotide-diphospho-sugar glycosyltransferases based on amino acid sequence similarities. Biochem J. 1997;326 ( Pt 3)(Pt 3):929-39. DOI:10.1042/bj3260929u |
12. Coutinho PM, Deleury E, Davies GJ, and Henrissat B. (2003). An evolving hierarchical family classification for glycosyltransferases. J Mol Biol. 2003;328(2):307-17. DOI:10.1016/s0022-2836(03)00307-3 |
13. Claus-Wilhelm von der Lieth, Thomas Luetteke, and Martin Frank. (2010-01-19) Bioinformatics for Glycobiology and Glycomics: An Introduction. Wiley.

    Chapter 5: Coutinho PM, Rancurel C, Stam M, Bernard T, Couto FM, Danchin EGJ, Henrissat B. "Carbohydrate-active Enzymes Database: Principles and Classification of Glycosyltransferases."#Garron2010 pmid=20805221

14. Lombard V, Bernard T, Rancurel C, Brumer H, Coutinho PM, and Henrissat B. (2010). A hierarchical classification of polysaccharide lyases for glycogenomics. Biochem J. 2010;432(3):437-44. DOI:10.1042/BJ20101185 |
15. Levasseur A, Drula E, Lombard V, Coutinho PM, and Henrissat B. (2013). Expansion of the enzymatic repertoire of the CAZy database to integrate auxiliary redox enzymes. Biotechnol Biofuels. 2013;6(1):41. DOI:10.1186/1754-6834-6-41 |