Comparative studies of alpha-lactalbumin and lysozyme: the proteins of kangaroo (Megaleia rufa and Macropus giganteus) and horse (Equus caballus).

As part of a study of the 'whey' proteins of various mammals, a comparison is made of the alpha-lactalbumins and lysozymes of the kangaroo and horse. In the milk of the red kangaroo (Megaleia rufa) there is only one alpha-lactalbumin and it occurs throughout lactation, but no lysozyme has been detected. There are two alpha-lactalbumins in the milk of the grey kangaroo (Macropus giganteus), one, designated alpha-lactalbumin Zone B, is present throughout lactation; the second, designated alpha-lactalbumin Zone A, is present only in late lactation. One lysozyme is also present. The milk of the horse (Equus caballus) contains one alpha-lactalbumin and at least one lysozyme. Partial amino acid sequences are proposed from sequence determination and from analyses of tryptic peptides compared with the known sequences of other alpha-lactalbumins and lysozymes.