Alpha-Lactalbumin (aLA)

Alpha-lactalbumin is an important whey protein in cow's milk (~1 g/l), and is also present in the milk of many other mammalian species. In primates, alpha-lactalbumin expression is upregulated in response to the hormone prolactin and increases the production of lactose. Alpha-lactalbumin forms the regulatory subunit of the lactose synthase (LS) heterodimer and beta-1,4-galactosyltransferase (beta4Gal-T1) forms the catalytic component. Together, these proteins enable LS to produce lactose by transferring galactose moieties to glucose. As a monomer, alpha-lactalbumin strongly binds calcium and zinc ions and may possess bactericidal or antitumor activity. A folding variant of alpha-lactalbumin, called HAMLET, likely induces apoptosis in tumor and immature cells.