LYZ1

Alpha-lactalbumin / lysozyme C
LYZ1
SMART accession number:SM00263
Description:
Interpro abstract (IPR001916):

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 (PUBMED:7624375), (PUBMED:8535779). This classification is available on the CAZy (CArbohydrate-Active EnZymes) web site. Because the fold of proteins is better conserved than their sequences, some of the families can be grouped in 'clans'.

Glycoside hydrolase family 22 comprises enzymes with two known activities; lysozyme type C (EC 3.2.1.17) and alpha-lactalbumins. Asp and/or the carbonyl oxygen of the C-2 acetamido group of the substrate acts as the catalytic nucleophile/base.

Lysozyme type C and alpha-lactalbumin and are similar both in terms of primary sequence and structure, and probably evolved from a common ancestral protein. There is, however, no similarity in function as lactalbumin promotes the conversion of galactosyltransferase to lactose synthase and is essential for milk production (PUBMED:6715332), while lysozyme catalyses the hydrolysis of bacterial cell wall polysaccharides; it has also been recruited for a digestive role in certain ruminants and colobine monkeys (PUBMED:2738070). Another significant difference between the two enzymes is that all lactalbumins have the ability to bind calcium (PUBMED:3785375), while this property is restricted to only a few lysozymes (PUBMED:3666156).

The binding site was deduced using high resolution X-ray structure analysis and was shown to consist of three aspartic acid residues. It was first suggested that calcium bound to lactalbumin stabilised the structure, but recently it has been claimed that calcium controls the release of lactalbumin from the golgi membrane and that the pattern of ion binding may also affect the catalytic properties of the lactose synthetase complex.

GO component:extracellular region (GO:0005576)
Family alignment:
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There are 411 LYZ1 domains in 398 proteins in SMART's nrdb database.

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