EFFECT OF DENATURANT AND COSOLVENTS ON THE STABILITY OF WHEAT-GERM LIPASE

Purified wheat germ lipase has a specific activity of 12 +/- 1 units, and the addition of urea decreases the activity of the enzyme. Partial specific volume of the enzyme in presence of 8 M urea is 0.723 and 0. 717 mL/g for isomolal and isopotential measurements, respectively, and the preferential interaction parameter (xi(3)) value is 0.05 g/g. Ult raviolet and fluorescence emission measurements indicated the exposure of aromatic amino acid residues from the interior of the protein, and thermal denaturation temperature (T-m) measurements indicated a decre ased stability of the enzyme by 12 degrees C from a control value of 5 6 degrees C. The addition of specific cosolvents was found to increase the thermal stability of the enzyme to different extents (patent pend ing). The concentration of the cosolvent (10-40%) used has a direct ef fect on the retention of activity of the enzyme after being exposed to elevated temperatures in the presence of these cosolvents.