Abstract
Decomposition of major milk protein fractions by milk protease was investigated by determination of liberated tyrosine and by polyacrylamide get electrophoresis (PAE). The rate of liberation of tyrosine from unfractionated casein, αs-casein and κ-casein was similar, but that from β-casein was about half of that from other caseins. However, β-casein showed drastic changes in PAE pattern. Two of the decomposed products of β-casein seemed to have the equal mobility to temperature-sensitive and R-(or γ-) casein, respectively. Decomposed products of κ-casein gave the pattern similar but not identical to para-κ-casein. No significant change occurred in PAE patterns when unfractionated whey protein, β-lactoglobulin and α-lactalbumin were incubated with milk protease.
