Improvement of Physicochemical and Enzymatic Properties of Bovine Trypsin by Non-enzymatic Glycation

Bovine trypsin was modified with glucose through the Maillard reaction at 50°C and 65% RH for various periods (1 to 8 days). Tryptic activity against both benzoyl-L-arginine-p-nitroanilide and two protein substrates was enhanced with increases in the reaction period, and reached the maximum after a 4-day reaction. Although there were no big differences in pH dependency of trypsin activity between native and modified trypsins, the Km of the modified trypsin decreased to about half the native one. The modified trypsin retained its original activity almost completely after incubation in a buffer solution of pH 8.0 at 37°C for 72 h, while native trypsin was greatly inactivated. Furthermore, tryptic acitivity at high temperature, residueal activity after heating, and differential scanning calorimetric analysis showed that the modified trypsin was more heat-stable than native trypsin.