Glycoside hydrolase family 56

In molecular biology, glycoside hydrolase family 56 is a family of glycoside hydrolases.

Glycoside hydrolases 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 glycoside hydrolases, based on sequence similarity, has led to the definition of 100 different families. This classification is available on the CAZy web site, and also discussed at CAZypedia, an online encyclopedia of carbohydrate active enzymes.

Glycoside hydrolase family 56 CAZY GH_56 includes enzymes with hyaluronidase activity. The venom of Apis mellifera (Honeybee) contains several biologically-active peptides and two enzymes, one of which is a hyaluronidase. The amino acid sequence of bee venom hyaluronidase contains 349 amino acids, and includes four cysteines and a number of potential glycosylation sites. 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.

PH-20 is required for sperm adhesion to the egg zona pellucida; it is located on both the sperm plasma membrane and acrosomal membrane. The amino acid sequence of the mature protein contains 468 amino acids, and includes six potential N-linked glycosylation sites and twelve cysteines, eight of which are tightly clustered near the C-terminus.