Utilization of Immobilized Trypsin on Commercial Silica Gel as Catalyst.

In this study, trypsin was immobilized onto commercial silica gel and the transesterification of N-acetyl-L-tyrosine ethyl ester (ATEE) and 1-propanol in an organic solvent was used as a model reaction. The amount of trypsin adsorbed onto the support affected the time required to achieve full conversion. The concentration of immobilized trypsin that provided a maximum yield of product in a minimal amount of time was 43 (imol of trypsin/g silica gel. At the end of transesterification reactions, the turnover frequency (9.3 · 10-5 to 6.8 · 10-1 s-1) and turnover number (8 to 520) of transesterification markedly increased when the initial concentration of the substrate had increased from 0.8 to 100 mmol L-1. The kinetic parameters Km (64.8 mmol L-1 ATEEinitial) and Kmax (0.364 mmol L-1 ethanol min-1) were determined. The immobilized trypsin maintained enzymatic activity and reusability after one month of storage at 4 °C. [ABSTRACT FROM AUTHOR]