Effects of Ca 2+ on catalytic activity and conformation of trypsin and α-chymotrypsin in aqueous ethanol

Abstract

The effects of calcium ions on the conformation and catalytic activity of trypsin and α-chymotrypsin were studied in aqueous ethanol. The activity of α-chymotrypsin was practically lost within 10 min in the presence of 60% ethanol while trypsin preserved about 40% of its original activity even in 85% ethanol at pH 3. The catalytic activity of α-chymotrypsin did not decrease in the presence of 1.2 M CaCl 2 and 0.6 M CaCl 2 with trypsin in ethanolic solvent. In the latter case an activation of enzyme was observed. The stabilizing effects of calcium ions were accompanied by an increase in the helical content in both enzymes, as followed by circular dichroism measurements.