Thermolysin‐catalyzed peptide synthesis in aqueous polymer two‐phase systems

Abstract A proteolytic enzyme, thermolysin, was covalently immobilized to dextran which has a small number of carboxyl groups. Enzymatic synthesis of aspartame derivative (Boc‐Asp‐Phe‐OMe) using the dextran‐conjugated thermolysin was carried out in an aqueous polymer two‐phase system, where poly(ethylene glycol) (PEG) and dextran dissolved in water make a phase separation. The yield of the peptide catalyzed by the dextran‐conjugated thermolysin was higher than that using a native enzyme in the aqueous polymer two‐phase system partly due to the effect of the microenvironment around the modified enzyme and partly due to the “mass‐law” effect (the preferential dissolution of the peptide product into the PEG phase). The aqueous polymer two‐phase system would be very useful to carry out enzymatic organic syntheses in high yields.