New to the CAZy classification? Read this first.
Want to learn more about CAZypedia? Read the CAZypedia 10th anniversary article in Glycobiology.
Glycoside Hydrolase Families
This page lists all the Glycoside Hydrolase (GH) Family pages in CAZypedia that have been given Curator Approved status, as well as those that are currently under construction, unassigned (i.e. lacking a Responsible Curator and Author), or deleted.
The term glycoside hydrolase (GH) (alternatively, glycosidase) formally refers to enzymes that catalyze the hydrolytic cleavage of the glycosidic bond to give the carbohydrate hemiacetal. Detailed explanations of the distinct catalytic mechanisms employed by these enzymes can be found on the glycoside hydrolase lexicon page. Since the seminal sequence-based classification of GHs into families, it has subsequently been observed that some of these families also group non-hydrolytic enzymes and proteins, due to sequence and structural similarity [1, 2, 3, 4, 5, 6, 7, 8]. In many cases, these alternative activities bear some degree of mechanistic similarity (e.g., conserved catalytic residues or enzyme intermediates) to the eponymous enzymes:
- Transglycosylases are mechanistically related to retaining glycoside hydrolases, with the exception that a sugar (or another nucleophile), rather than water, acts as the acceptor substrate to yield glycosidic bond exchange.
- Phosphorylases cleave glycosidic bonds using phosphate as a nucleophile to yield sugar-1-phosphates; this reaction is readily reversible, allowing the synthesis of glycosidic linkages. Sequence classifies many, but not all (see glycosyltransferases for exceptions) phosphorylases with retaining or inverting glycoside hydrolases.
- Alpha-glucan lyases are found within family GH31 and degrade α-(1-4)-linked glucans (e.g. starch) and oligosaccharides via an elimination mechanism that yields an enol (unsaturated) product that tautomerises to its keto form, 1,5-anhydro fructose.
- NAD-dependent glycoside hydrolases of families GH4 and GH109 use nicotinamide adenine dinucleotide as redox cofactor to activate the sugar ring for glycosidic bond cleavage by elimination.
Responsible Curator as essentially complete. CAZypedia is a living document, so further improvement of these pages is still possible; please see the individual pages for more information.
There are currently 112 Curator approved Glycoside Hydrolase (GH) Family pages in CAZypedia.
under construction in CAZypedia. As such, the Responsible Curator has deemed that the page's content is not quite up to CAZypedia's standards for full public consumption. All information on these pages should therefore be considered to be under revision and may be subject to major changes.
There are currently 8 Glycoside Hydrolase Family pages under construction in CAZypedia.
Unassigned pages are currently lacking a Responsible Curator and one or more Authors. If you are an expert on any of these families and would like to help us improve CAZypedia by getting involved with the production and maintenance of the corresponding page(s), please contact a member of the Board of Curators directly, or via this form.
There are currently 29 Glycoside Hydrolase Family pages in CAZypedia that have not been assigned to a Responsible Curator.
There are currently 6 pages in CAZypedia that describe Glycoside Hydrolase families deleted from the CAZy DB.
- Henrissat B. A classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem J. 1991 Dec 1;280 ( Pt 2):309-16.
- Henrissat B and Bairoch A. New families in the classification of glycosyl hydrolases based on amino acid sequence similarities. Biochem J. 1993 Aug 1;293 ( Pt 3):781-8.
- Henrissat B and Bairoch A. Updating the sequence-based classification of glycosyl hydrolases. Biochem J. 1996 Jun 1;316 ( Pt 2):695-6.
- Henrissat B and Davies G. Structural and sequence-based classification of glycoside hydrolases. Curr Opin Struct Biol. 1997 Oct;7(5):637-44.
- Davies, G.J. and Sinnott, M.L. (2008) Sorting the diverse: the sequence-based classifications of carbohydrate-active enzymes. The Biochemist, vol. 30, no. 4., pp. 26-32. Download PDF version.
- Davies G and Henrissat B. Structures and mechanisms of glycosyl hydrolases. Structure. 1995 Sep 15;3(9):853-9. DOI:10.1016/S0969-2126(01)00220-9 |
- Vocadlo DJ and Davies GJ. Mechanistic insights into glycosidase chemistry. Curr Opin Chem Biol. 2008 Oct;12(5):539-55. DOI:10.1016/j.cbpa.2008.05.010 |
- Yip VL and Withers SG. Breakdown of oligosaccharides by the process of elimination. Curr Opin Chem Biol. 2006 Apr;10(2):147-55. DOI:10.1016/j.cbpa.2006.02.005 |