Isolation of κ-CN-1P and β-CN-5Р fractions from native casein micelles

Proteins of the casein complex of milk arouse considerable interest as the precursors of biologically active peptides which are capable of influencing various physiological systems of the body (digestive, nervous, cardiovascular, and immune). It has been established that various bioactive peptides are unevenly located in the structure of casein fractions. In this connection, there appeared a need to separate individual fractions of this protein for studying the pathways of formation and properties of bioactive casein peptides. To minimize negative effects of the purification procedure, we used the gel filtration on Sefarose 2B to produce native casein micelles and repeating filtration on Sephadex G-150 to separate individual fractions. As a result, according to electrophoretic analysis, casein micelles with a characteristic protein composition were obtained. Taking into account the similarity of the molecular weight of components for their dividing the repeated gel filtration was carried out with separating the chromatograms into sectors. The composition of the combined fractions of each sector was analyzed by electrophoresis. This approach allowed isolating two electrophoretically homogeneous proteins from native casein micelles – κ-CN-1P and β-CN-5P, as well as to obtain a substantially purified (> 83%) αS1-CN-XP. Isolated caseins without the influence of extreme factors can be used to study natural bioactive peptides