O-Glycosyl hydrolases (EC 3.2.1.-) are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [PMID:7624375, PMID:8535779, PUB00005672]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [PUB00007032]. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in 'clans'.

O-Glycosyl hydrolases (EC 3.2.1.-) are a widespread group of enzymes that hydrolyse the glycosidic bond between two or more carbohydrates, or between a carbohydrate and a non-carbohydrate moiety. A classification system for glycosyl hydrolases, based on sequence similarity, has led to the definition of 85 different families [PMID:1747104, PMID:8352747, PMID:8687420, PMID:1732212, PMID:8535779, PUB00005672]. This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site [PUB00007032]. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in 'clans'.

Family 56 (CAZY: GH_56) encompasses a group of hyaluronidases (EC: 3.2.1.35) that includes venom hyaluronidases [PMID:7682712] and mammalian sperm surface proteins (PH-20).

Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, stings, drugs, or food) that, in most people, result in no symptoms. A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans [WHO/IUIS Allergen Nomenclature Subcommittee King T.P., Hoffmann D., Loewenstein H., Marsh D.G., Platts-Mills T.A.E., Thomas W. Bull. World Health Organ. 72:797-806(1994)]. This nomenclature system is defined by a designation that is composed of the first three letters of the genus; a space; the first letter of the species name; a space and an arabic number. In the event that two species names have identical designations, they are discriminated from one another by adding one or more letters (as necessary) to each species designation.

The allergens in this family include allergens with the following designations: Api m 2, Dol m 2 and Ves v 2.

The venom of Apis mellifera (honeybee) contains several biologically-active peptides and two enzymes, one of which is a hyaluronidase [PMID:7682712]. The amino acid sequence of bee venom hyaluronidase contains 349 amino acids, and includes four cysteines and a number of potential glycosylation sites [PMID:7682712]. The sequence shows a high degree of similarity to PH-20, a membrane protein of mammalian sperm involved in sperm-egg adhesion, supporting the view that hyaluronidases play a role in fertilisation [PMID:7682712].