Lactalbumin, alpha-, also known as LALBA, is a protein which in humans is encoded by the LALBA gene a-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. a-lactalbumin forms the regulatory subunit of the lactose synthase (LS) heterodimer and ÃŸ-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. When formed into a complex with Gal-T1, a galactosyltransferase, a-lactalbumin enhances the enzyme's affinity for glucose by about 1000 times, and inhibits the ability to polymerise multiple galactose units. This gives rise to a pathway for forming lactose by converting Gal-TI to Lactose synthase.