Glycosidation of trypsin with end-group activated dextran

A monoaminated dextran derivative was attached to trypsin via a carbodiimide-catalyzed reaction. The modified enzyme contained 3 mol of polysaccharide per mol of protein, and retained about 93% and 85% of the native esterolytic and proteolytic activity, respectively. The thermostability was enhanced from 49.7 to 67.4°C for modified trypsin. The activation free energy of thermal inactivation at 55°C was increased by 7.2 kJ/mol for the protease after modification with the polymer. The improved conformational stability of trypsin after glycosidation with dextran was confirmed by fluorescence spectroscopy. The glycosidated protease retained 70% of its initial activity after 3 h incubation at pH 9.0.