Glycosidation of phenylalanine dehydrogenase with O-carboxymethyl-poly-β-cyclodextrin

The polysaccharide O-carboxymethyl poly-β-cyclodextrin (M = 1.3 × 104, 40% COOH groups) was employed as modification agent for Bacillus badius phenylalanine dehydrogenase via a carbodiimide-catalyzed reaction. The neoglycoenzyme retained 63% of its initial activity and contained about 2.5 mol of polymer per mole of enzyme. The optimum temperature for the enzyme was increased by 15 °C and its thermostability was improved by about 6 °C over 10 min incubation. The conjugate was also more resistant to thermal inactivation at different temperatures, ranging from 45 to 60 °C. The improved conformational stability of the modified enzyme was confirmed by fluorescence spectroscopy.