Nomenclature of the Proteins of Cow's Milk: Fourth Revision

Abstract

This report reviews the nomenclature of the milk proteins of cow''s milk in light of more recent advances. With the establishment of the primary structures of a number of these proteins, a definite identification of .alpha.S1-, .kappa.-, .beta.- and the .gamma.-caseins and .beta.-lactoglobulin and .alpha.-lactalbumin is now possible. On the basis of new information on their primary structures and relationship to .beta.-casein polymorphs, changes in nomenclature were recommended for proteins of the .gamma.-casein fraction. Although the primary structure serves as the unambiguous definition of proteins for which it is known, a more practical identification is necessary. The behavior in gel electrophoresis under suitable conditions should be employed for this purpose for all of the major milk proteins of raw skim milk except the immunoglobulins, where because of their heterogeneity and molecular genetics, physical parameters are less useful, and their identification must be based upon antigenic determinants and their homology with their human counterparts. More work is needed, and with the accumulation of more information, additional changes in nomenclature can be expected for such proteins as the minor components of .alpha.S- and .kappa.-caseins, .alpha.-lactalbumin and the proteose-peptone fraction as well as further confirmation of the presence of immunoglobulins IgE and additional IgG subclasses. Additional components and genetic variants also can be expected.