
%0 Journal Article
%A McKenzie, HA 
%A Wake, RG 
%T Studies of Casein. I. Some Observations on the Heterogeneity of Casein Fractions
%J Australian Journal of Chemistry
%D 1959/12/01
%V 12
%N 4
%P 712-722
%K 
%R https://doi.org/10.1071/CH9590712
%U https://www.publish.csiro.au/paper/CH9590712 
%X The heterogeneity of casein is discussed in the light of methods currently used for the fractionation of casein. In particular, the possible heterogeneity of certain preparations of &#945;-casein is considered. This is important because it has been generally considered that &#945;-casein is the protective colloid which is altered when the enzyme, rennin, acts on casein micelles. Recently, Waugh and von Hippel (1956) have suggested that their new component x-casein, and not &#945;-casein, is the protective colloid. These two viewpoints could be reconciled if &#945;-casein samples previously examined contained x-casein as well. In the present work, a study is made of filter paper electrophoresis, micelle-forming properties, and sedimentation of casein fractions. It is shown that x-casein is concentrated with &#945;-casein in fraction A during the alcohol fractionation method of Hipp et al. (1952). On the other hand fraction B contains &#945;-casein essentially free of x-casein. The a-casein obtained in the urea fractionation method of Hipp et al. also contains x-casein. Thus only alcohol fraction B is a suitable source of pure &#945;-casein.   During the paper electrophoretic examination of casein fractions a number of minor protein components are observed. A component moving more slowly than &#947;-casein is present in acid casein, second-cycle casein-fraction P, and an alcohol fraction. This component was first observed in the latter fraction by Hipp et al. (1952) when preparing &#947;-casein. Electropherograms of second-cycle casein-fraction S indicate the presence of x-, &#946;-, and &#947;-casein, and two minor components moving between x- and &#946; The way in which these components arise is briefly discussed. 
