CHEMICAL MODIFICATION OF ESCHERICHIA-COLI L-ASPARAGINASE WITH POLY(N-VINYLPYRROLIDONE-CO-MALEIC ANHYDRIDE)

E. coli L-asparaginase was modified with poly(N-vinylpyrrolidone-co-ma leic anhydride). The modified enzyme exhibited the decrease of immunor eactivity towards anti-asparaginase serum with increase of modificatio n degree. The immunoreactivity could be completely restrained although activity of the modified asparaginase was retained by 8.3% of the nat ive one at the highest modification degree. The modified asparaginase also showed much greater stability against protease. After one hour in cubation in presence of trypsin, the modified enzyme retained about 80 % of its original activity while the native enzyme retained only 14%. As a result of modification the pH optimum of enzyme activity shifted by about 0.8 pH unit in the alkaline direction. The apparent optimum t emperature of the modified enzyme was about 10 degrees C higher than t hat of native enzyme.