alphalactalbumin

Alpha-lactalbumin, also written as α-lactalbumin, is a small calcium-binding whey protein found in the milk of mammals, with particular prominence in human milk. The mature protein is about 14 kDa and comprises roughly 123 amino acids, stabilized by four disulfide bonds. It is one of the major whey proteins, alongside beta-lactoglobulin, and is abundant in milk during lactation.

Functionally, alpha-lactalbumin serves as the regulatory subunit of lactose synthase in the mammary gland, partnering with beta-1,4-galactosyltransferase to catalyze lactose production from UDP-galactose and glucose-1-phosphate. Calcium binding helps maintain its folded structure and activity. Expression levels vary by species and stage of lactation.

Structurally, the protein has a compact, two-domain fold and high thermal stability, partly due to its disulfide network. Its amino acid composition includes a relatively high content of tryptophan, a feature exploited in nutritional applications such as infant formulas designed to more closely resemble human milk.

In research and application, alpha-lactalbumin is used commercially as a dietary protein supplement and is often enriched in infant formulas. It is also studied for antimicrobial properties and for forming HAMLET (human alpha-lactalbumin made lethal to tumor cells) complexes with oleic acid, which have shown tumoricidal activity in laboratory studies. It is generally regarded as safe for consumption, though individuals with milk allergy may react. Alpha-lactalbumin is produced in lactating mammary glands and released into milk, where it can be isolated from whey during dairy processing.