Determination of the influence of the pH of hydrolysis on enzyme selectivity of Bacillus licheniformis protease towards whey protein isolate

Abstract

Enzymatic protein hydrolysis is typically described by the degree of hydrolysis and by the enzyme specificity. While the specificity describes which cleavage sites can potentially be cleaved, it does not describe which are preferred. To identify the relative rate at which each individual cleavage site is hydrolysed, enzyme selectivity has recently been introduced. To test the effect of pH on selectivity, whey protein isolate (WPI) was hydrolysed with Bacillus licheniformis protease (BLP) at pH 7.0, 8.0 or 9.0. At all pH values, large differences in the enzyme selectivity (from <0.004% to 27%) towards the different cleavage sites of β-lactoglobulin were observed. The changes in selectivity as a function of pH were significant (up to 80% increase or decrease). This significant variation in selectivity shows that this parameter may be useful in understanding peptide release kinetics in enzymatic hydrolysis under different conditions.