UV Sensitivity of Free and Immobilized on Chitosan Matrix Proteases

Abstract

UV irradiation is an essential factor in natural and artificial climate in modern environmental conditions, which has a constant effect on living systems. Collagenase, bromelain, ficin, papain («Sigma-Aldrich») and trypsin («MP biomedicals») were the objects of this study. The substrate for hydrolysis was BSA («Sigma-Aldrich»), the carriers for immobilization were chitosans (< 100, 200 and 350 kDa) and chitosan succinate («Bioprogress»). The protease immobilization was carried out by the adsorption. The determination of the protein amount in samples and their catalytic activity was carried out by the modified Lowry method. UV irradiation of proteases was performed using doses 151-6040 J/m 2 . By the degree of photosensitivity, hydrolases can be arranged in the next row: collagenase → bromelain → ficin → papain → trypsin. Adsorption on a chitosan and succinate of chitosan leads to an increase in the stability to ultraviolet light of heterogeneous (immobilized) biocatalysts compared to free enzymes. Photoprotective effect of the chitosan may be due to the following reasons: enzyme interact with the chitosan to form photo resistant complexes; сhitosan screen active free-radicals, preventing the photooxidation of a certain number of amino acids, including the active centers of the studied enzymes under the influence of UV irradiation.