Enhanced enzymatic activity and stability of trypsin by reductive alkylation in solid phase

Amino groups of trypsin (EC 3.4.21.4) were reductively alkylated in solid phase to obtain a surface‐active and biologically active enzyme in an o/w emulsion system. Trypsin adsorbed on a benzamidine–sepharose column was reductively alkylated with n‐octanal in the presence of sodium borohydride, i.e., trypsin‐C8. Activity of trypsin‐C8 against Nα‐benzoyl‐L‐arginine‐p‐nitroanilide was three times higher than that of native trypsin. Activities of trypsin and trypsin‐C8 against casein were almost the same. After incubating the trypsin solution at 40°C for 1 h, residual activities in the emulsion and solution systems were 64.2 and 57.4%, respectively. On the other hand, residual activities of native trypsin following incubation were 21.8% in the emulsion system and 33.2% in the solution system. Enhancement of trypsin‐C8 stability in the emulsion system may derive from interaction between the hydrophobic areas of trypsin‐C8 molecules and the hydrophobic phase of the emulsion.