Immobilization of α-Chymotrypsin on zeolite for peptide synthesis in organic solvent

We used zeolite immobilized α-chymotrypsin for peptide synthesis in dichloromethane. HY, NH4Y, NaY, HNH4DAY, HDAY and MCM-41 zeolites with different acidity and different pore sizes were compared with the synthesis of ZTyrGlyGlyOEt as a model reaction. The reusability of the six different zeolites was studied, and the results showed that HY zeolite was the best matrix for immobilization of α-chymotrypsin; dealusminized Y zeolites and MCM-41 were not better supports for enzymatic reaction than Y zeolites. It was suggested that the activity of immobilized α-chymotrypsin depended greatly on the strength of the H-bond of the zeolite-enzyme complex, and had little to do with the pore dimension of the zeolite. The activity of immobilized enzyme and product yield were influenced significantly by the water content of dichloromethane. A little water around the enzyme molecules is truly necessary to maintain its activity. There are also many questions raised about the reaction such as how to identify the H-bond formation between enzyme and zeolite, and how to hold the enzyme tightly to zeolite. All of the above problems need to be studied further.