Chemistry and biological function of α‐lactalbumin

α‐Lactalbumins, a family of low molecular weight single‐chain globular proteins, are synthesized under hormonal control by the mammary glands of all mammals capable of lactose synthesis shortly before and after parturition and make up to 0.12% (w/v) of the final secretory product, i.e., the milk. The most intensively characterized of all are the bovine α‐lactalbumins from various species in terms of the molecular size, amino acid composition and sequence, immunological cross‐reactivity, and even their capacity to modify the rate of galactosyltransferase activity. ?‐Lactalbumins and lysozymes exhibit considerable degree of amino acid sequence (primarily structure) homology and similarity in their covalent structures. The up‐to‐date theoretical and experimental reports on the similarity of molecular conformations and three‐dimensional structures of the two families of proteins, presumably of common ancestry, are more transgressive than confirmatory at the present time. The preceding facts, along with the recognition of the α‐lactalbumin‐galactosyltransferase interaction as a special example of a two‐component biochemical catalytic system and the control of lactose and presumably of glycoprotein biosynthesis by α‐lactalbumin, have generated a great deal of research interest and academic curiosity among food biochemists and molecular biologists. This review is an attempt to meet with the naturally ensuing demand for examining the older literature and critically summarizing the new findings on the biosynthesis, biochemistry, and the molecular biology of α‐lactalbumins. It also includes comparative discussions on the chemistry and the molecular evolution of α‐lactalbumins and lysozymes.