Abstract: Recently, scientists have found that milk and some other proteins were possible precursors of many different biologicalactive peptides. These peptides are inactive within the sequence of the precursor proteins and can be released from theprecursor when treated with proteinase under proper conditions such as pH, temperature and ionic concentration. Up to now,several kinds of biological peptides have been found from the proteolysis solution of nutritious or seed proteins. Because ofthese proteins were very cheap, rich in resources and safe for health, the bioactive peptides thereby have had commercialpotential, also been suitable to scale up. Therefore the degree of hydrolysis, digest conditions and the relationship between themacromolecule proteins substrates and the proteinases were investigated in several experiments in this paper. The resultsshowed that when the concentration of the substrate increased over some point, the rates of reactions will decrease on thecontrary. It was obviously deferent to the Michaelis-Menton Equation. It showed that the interactions between enzymes andsubstrates of macromolecular proteins might be more complex.

Key words: casein, degree of hydrolysis(DH), substrates of macromolecular proteins, bioactive peptides, proteinase