<p>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 weights of 200 and 350 kDa, entrapment in chitosan (&lt;100 kDa) and chitosan succinate 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 decreased by 72%. After immobilization, the stability of the enzyme complex under the above conditions increased: the activity of trypsin immobilized on the matrix of chitosans with molecular weights of 200 and 300 kDa was maintained at the level of about 75%, after entrapment of the enzyme in the chitosan gel (&lt;100 kDa), by up to ~50%, and chitosan succinate, by 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 determines the photoprotective properties of these 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 these polysaccharides is maintained.</p>