Comparative aspects of milk proteins

Abstract

The current status of knowlege of the major proteins of milks of various species is evaluated. Most of the non-bovine milk proteins are homologous with the recognized families of those ofBos taurus, α_s1-caseins, α_s2-caseins, β-caseins, K-caseins, β-lactoglobulins, and α-lactalbumins, each family representing a separate genetic locus specific to the mammary gland. No prominent milk protein not homologous to one of these families has yet been discovered in milk of any species. Genetic polymorphism resulting from substitutions in the polypeptide chains and various degrees of post-translational phosphorylation, glycosylation, and proteolysis have been identified in milk proteins of several species. Total protein production ranges among species from about 0.5 to 10 g/d per kg^0.75maternal weight. Proportions of the several proteins vary greatly among species, but few accurate analytical data are available except for total casein and total whey protein contents.