Stabilization of a-chymotrypsin by modification with b-cyclodextrin derivatives

Bovine pancreatic a-chymotrypsin was chemically modified with two different b-cyclodextrin derivatives, named mono-6-formyl-bcyclodextrin and mono-6-succinyl-6-deoxy-b-cyclodextrin. The modified enzymes contained approx. 3-5 mol of oligosaccharide/mol of protein, and retained full proteolytic and esterolytic activity. The optimum temperature for a-chymotrypsin was increased by 8 °C and its thermostability was enhanced by about 4-6 °C after modification. The conjugated enzymes were also more resistant to thermal inactivation at temperatures ranging from 45 to 55 °C. Additionally, the modified enzymes were 7-fold more stable against incubation at pH 9.0. The possible influence of supramolecular interactions on the thermal stabilization of modified a-chymotrypsins was also studied.