Studies on κ-Casein of Bovine Milk II : Heterogeneity of κ-casein (Agricultural Chemistry)

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  • 不均一性
  • フキンイツセイ
  • 牛乳のκ- カゼインに関する研究 II : 不均一性(農芸化学部門)

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Abstract

Heterogeneity of κ-casein prepared by various methods was investigated using disc electrophoresis, starch-agar gel electrophoresis, agarose gel electrophoresis, starch-agarose gel electrophoresis, DEAE cellulose chromatography, Sepharose 6B gel filtration and isoelectric focusing. Results suggest that all the κ-caseins, regardless of their preparative methods, were more or less heterogeneous and that the heterogeneity depends upon at least two factors; molecular size and charge. The result of DEAE cellulose chromatography shows that κ-casein could dissociate into two components one of which seemed to be a para-like κ-casein. The para-like κ-casein had been impossible to identify by standard starch gel electrophoresis or by disc electrophoresis. Therefore, it does not seem to be a simple impurity, but seems to be a component which forms a κ-casein complex. Although random S-S bonds have been thought to be a unique cause for the heterogeneity of κ-casein, variation in the amount of para-like κ-casein may be another cause. The little deviation in the concentration of para-like κ-casein seems to indicate that it was in the original milk and was not an artifact produced during preparation. It was also found that the κ-casein molecules were the largest and the least heterogeneous when prepared by the urea sulfuric acid method. On the other hand, κ-casein prepared by the calcium ethanol method seemed to be somewhat unfolded into smaller units and to release para-like κ-casein most easily.

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