Improvement of enzymological properties of pepsin by chemical modification with chitooligosaccharides

In order to improve the enzymological properties and to enhance the stability of pepsin (PP, EC 3.4.23.1), chitooligosaccharide (COS) was used to chemically modify enzyme molecules of PP. The results showed that one protein band appeared on the PAGE diagram, indicating that the enzyme samples reached electrophoresis purity after purification. The molecular weights of the enzymes before (PP) and after (COS-PP) modification were 38.68 KD and 49.55 KD, respectively. The Km and Vmax of PP were 2.40 mg/mL and 1.1 × 106 mg/(mg Pro min). The Km and Vmax of COS-PP were 4.44 mg/mL and 8.3 × 105 mg/(mg Pro min), respectively. The optimal pH values of PP and COS-PP were 1.5-2.0. The optimal temperatures of PP and COS-PP were 57 °C and 59 °C, respectively. After being incubated at 60 °C for 1 h, the residual activities of PP and COS-PP solutions were 26.56% and 74.72%, respectively. After being incubated at 65 °C for 1 h, the residual activities of PP and COS-PP solutions were 14.74% and 46.40%, respectively. After being kept at room temperature (25 °C) or 4 °C refrigerator for 4 days, PP solution had basically no activity, whereas the residual activities of COS-PP solutions were 5.40% and 33.94%, respectively.