No abstract

No abstract

No abstract

Summary -The correlation between change of conformation of a-Iactalbumin and its degradation by gastric enzymes was verified. With citrate buffer (0.1 M), the modification of a-Iactalbumin conformation occurred when the pH value was below pH 4.0. This conformational change was influenced by buffer composition and ionic strength. However, the presence of EDTA in the butter did not modify the pH value at which the change of conformation of the protein occurred. Concomitantly, hydrolysis of a-Iactalbumin by bovine and porcine pepsins A and rennet was observed at pH values corresponding to the change in conformation of the protein. However, with chymosin, under the same pH and ionie strength conditions there was no significant hydrolysis of a-Iactalbumin.

The amino acid sequence of porcine and human caseinomacropeptides (CMP), the C-terminal glycopeptide released from kappa-casein by chymosin at the initial step of milk coagulation, have been investigated. The complete amino acid sequence of porcine CMP and that of the first 59 amino acid residues of human CMP have been determined. Porcine and human CMPs contain 71 and likely 65 amino acid residues respectively. The extra hexapeptide 38-43 found in porcine CMP arises obviously from the duplication of the DNA fragment coding for the 6 preceding amino acids.