Abstract
Glucose isomerase (Streptomyces phaeochromogenus) was immobilized on polyacrilonitrile by amidination reaction of the amino group of the enzyme with methylimidate hydrochloride produced on the resin. The immobilized proteins gave a dull maximum ranging from pH 8 to 9 vs. pH of the reaction bath at ca. 40°C and also gave a dull maximum at 60°C and a considerable decrease over 60°Cvs. the temperature of the immobilization reaction. However, the activity of the immobilized enzyme was gradually decreased vs. the elevation of the temperature from 30°C in so far as the present experiments were concerned. The activity of the immobilized enzyme was ca. 44% of the equivalent amount of the native enzyme on the average. The pH-activity pattern of the immobilized enzyme was almost identical to that of the native enzyme. However, the stable pH range of the preincubation bath for the immobilized enzyme was narrower than that of the native enzyme indicating the sharp drop of activity at both sides of pH. The optimum reaction temperature of the immobilized enzyme for the isomerization was almost identical to that of the native one, and the values of 20.1 and 19.6 kcal/mol were obtained for the apparent activation energy of the immobilized and the native enzymes, respectively. And, the heat stability of the immobilized enzyme was shown in the earlier decrease of its activity vs. the incubation temperature exceeding 60°C as compared to those of the native one. The durability of the immobilized enzyme was illustrated as the decrease of its activity vs. the repeat number of the activity test at 60 and 68°C, respectively. Their decay was found to be either due to the splitting off of the enzyme from the vehicle resin or due to the inactivation by the fatigue of the enzyme itself which depended on the bath temperature.