Lactalbumin (IPR000545)

Short name: Lactalbumin

Overlapping homologous superfamilies

Family relationships


Alpha-lactalbumin comprises 15 percent of the total human milk protein and is essential for lactose production [PMID: 3785375]. It is a globular calcium-binding metalloprotein secreted in the lactating mammary gland [PMID: 1920433], the calcium being bound in a novel binding loop that is superficially similar to the classic EF-hand motif. Lactalbumin attaches to beta-galactosyltransferase on the luminal surface of the Golgi apparatus, creating the lactose synthetase complex [PMID: 3785375], which catalyses the addition of galactose to glucose, forming lactose. 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. The lactalbumin gene also contains a novel upstream regulatory sequence called the `milk box' [PMID: 2845947], which is also found in genes of other milk proteins, and may be involved in either hormone regulation or tissue-specific expression in the lactating mammary gland. Alpha-lactalbumin is similar to C-type lysozyme in terms of primary sequence and structure [PMID: 6715332], and has probably evolved from a common ancestral protein. There is, however, no similarity in function.

GO terms

Biological Process

GO:0005989 lactose biosynthetic process

Molecular Function

GO:0005509 calcium ion binding
GO:0004461 lactose synthase activity

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.