Reversible Light-Stimulated Activation and Deactivation of α-Chymotrypsin by Its Immobilization in Photoisomerizable Copolymers

The enzyme α-chymotrypsin was immobilized in acrylamide copolymers which contain photoisomerizable components. The resulting enzyme-copolymer assemblies reveal photoswitchable “on-off” biocatalytic activities. Three kinds of acrylamide copolymers cross-linked with 4-(methacryloylamino)azobenzene (polymer 1) 1-[β-(methacryloxy)-ethyl]-3,3-dimethyl-6-nitrospiro[indoline-2,2′-[2H-l]benzopyran] (polymer 2), and bis[4-(dimethylamino)phenyl](4-vinylphenyl)methyl leucohydroxide (polymer 3) were used to immobilize the enzyme. The enzyme reveals bioactivity (position “on”) in the copolymer isomer states 1b, 2b, and 3b, respectively, while its activity is blocked (position “off”) in copolymers 1a, 2a, and 3a, respectively. The activity of the enzyme is assayed toward the hydrolysis of N-(3-carboxypropionyl)-L-phenylalanine p-nitroanilide (7). The photostimulated activities of the enzyme entrapped in the different copolymers correlate with the permeability properties of the substrate 7 across the photoisomer forms of the copolymers. While the copolymer isomer forms 1a, 2a, and 3a exhibit poor permeability toward the substrate 7, the copolymers 1b, 2b, and 3b are permeable toward the substrate 7.