Stability and catalytic properties of chemically modified pig trypsin

Pig trypsin was chemically modified with the bifunctional compound ethylene glycol-bis(succinic acid N-hydroxysuccinimide ester) to yield EG-trypsin. EG-trypsin showed greater thermal stability (100% active beyond 100 min at 55 degrees C; native only 53% active at 100 min) together with slightly increased tolerance toward some organic solvents. Arg/Lys hydrolysis ratio changed little. Esterase/amidase activity ratio of EG-trypsin in buffer was 11-fold greater than that of native pig trypsin, but 5-fold less in 30% v/v acetonitrile. In buffer, EG-trypsin synthesized the dipeptide benzoyl-Arg-Leu-NH2 at a 3-fold higher rate than native trypsin, but native trypsin outperformed EG-trypsin in 30% v/v acetonitrile.