Photoprotective Properties of Chitosan and Chitosan Succinate Against Trypsin at Different Methods of Enzyme Immobilization on Their Matrix

UV irradiation at doses of 3020, 4510, and 6040 J/m2 was found to decrease the level of specific activity of free trypsin by 28, 32, and 49%, respectively. Adsorption immobilization on the matrix of chitosans with molecular masses of 200 and 350 kDa, inclusion of chitosan (<100 kDa) and chitosan succinate in the gel contribute to the preservation of trypsin molecule activity at the level of ~90% and higher. Under UV irradiation in the dose range of up to 6040 J/m2 in the presence of a photosensitizer, methylene blue, at a concentration of 10–4 mol/l, the activity of free trypsin decreases by 72%. After immobilization, the stability of the enzyme complex under the above conditions increases: the activity of trypsin immobilized on the matrix of chitosans with molecular masses of 200 and 300 kDa is maintained at the level of about 75%, after inclusion of the enzyme in the chitosan gel (<100 kDa) – up to ~50%, chitosan succinate – up to ~70%. The molecular docking method revealed that a number of tryptophan, tyrosine and phenylalanine residues, as well as two cystines, take part in the formation of bonds and interactions between the trypsin molecule and the matrices of chitosan and chitosan succinate, which probably predetermines the photoprotective properties of the named polysaccharides. IR spectroscopy showed that after UV irradiation in the presence of methylene blue and without it, no significant changes in the wave number values in the region of the amide I, II and III bands were detected in the spectra of trypsin immobilized on chitosan and chitosan succinate matrices, which indicates that the stability of the enzyme structure in the complexes with the named polysaccharides is maintained.

UV irradiation, trypsin, chitosan, chitosan succinate, adsorption immobilization, inclusion in gel