lactalbumin

Lactalbumin refers to a family of calcium-binding proteins found in mammalian milk. The best characterized member is alpha-lactalbumin (ALA), a small, soluble whey protein that is abundant in human and bovine milk and has a mature mass of about 14 kilodaltons.

Alpha-lactalbumin is produced by mammary epithelial cells and released into milk. Its primary physiological role is as a regulatory subunit of lactose synthase, a complex with beta-1,4-galactosyltransferase. This complex converts glucose-1-phosphate and UDP-galactose into lactose, helping set the lactose content of milk. Lactose level influences osmotic balance and energy supply for the infant. Alpha-lactalbumin concentration varies by species and stage of lactation.

Structurally, alpha-lactalbumin is a compact, calcium-binding protein stabilized by multiple disulfide bonds. Calcium binding supports its correct folding and stability; the protein is sensitive to processing conditions such as heat, which can alter its structure and function.

It is a major whey protein alongside beta-lactoglobulin and is present in milk whey after casein removal. Commercially, alpha-lactalbumin is used in infant formulas to improve protein quality and amino acid balance and serves as a source of essential amino acids, notably tryptophan.

As a milk protein, alpha-lactalbumin is a potential allergen for individuals with milk protein allergies.

Research has described HAMLET (human alpha-lactalbumin made lethal to tumor cells), a complex of alpha-lactalbumin with oleic acid that can induce tumor cell death in vitro. These results are experimental and not an approved cancer treatment.

Industrial and research uses involve purification from milk whey or production by recombinant methods in microorganisms.