Reconstitution of Human Casein Micelle and Its Properties

Abstract

Human casein micelles were reconstituted from isolated κ- and β-caseins and calcium ions. Micelle formation was recognized in the presence of calcium chloride even at the low concentration of 5mM. At pH levels ranging from 5.5 to 8.0, the re-formed micelles were quite stable so that precipitation of β-casein was not observed. The large micelles were constituted by a higher ratio of β-casein to κ-casein (16:1 by weight) than the small micelles (3: 1). The κ-casein in the small micelles contained carbohydrates to about 43% (w/w) in the molecule, whereas that in the large micelles was only about 25%. When the casein micelles were re-formed from κ-easein and fractionated β-casein components, the extent of phosphorylation of the β-casein component was found to influence the micelle formation; i.e., the β-casein component with no phosphate (the 0-P form) was disadvantageous to form micelles, but the component with 5 phosphates (the 5-P form) formed micelles most easily.