Photocontrol of Organic Synthesis Using Immobilized Enzyme

Abstract

Application of hydrolytic enzyme to organic syntheses is attracting attention, because enzyme would promote selective reaction under moderate conditions. This paper describes an application of a protease to peptide synthesis with use of a photochromic compound and light energy.
A new photo-stable spiropyran, 3', 3'-dimethyl-8-methoxy-6-nitrospiro[2 H-1-benzopyran-2, 2'-indoline]-1'-propionic acid C 3 J was synthesized by the authors. The stability of photoresponsive activity was 3.4 times higher than that of 3', 3'-dimethyl-6-nitrospiro[2 H-1benzopyran-2, 2'-indoline]-1'-propionic acid 2 J (Fig.3). Improvement of the stability was mainly caused from introducing electron-donating groups at the ortho position.
α-Chymotrypsin was immobilized in collagen membrane modified with the spiropyran [3]. The enzyme-spiropyran-collagen membrane showed a reverse photochromism and catalyzed the synthesis of N-acetyl-L-phenylalanyl-L-phenylalanine ethyl ester from N-acetyl-L-phenylalanine and L-phenylalanine ethyl ester. As shown in Fig.4, the yield of the reaction for 55 h was 2% in the dark. In contrast, that for 35 h reached 6% under visible light (30000 lux). Under illumination, the spiropyran became an apolar state and the hydrophobicity of the enzyme bound membrane increased. Therefore, the synthetic reaction by the photosensitive immobilized enzyme was promoted by visible light irradiation.