Optimization of Immobilized Aldose Reductase Isolated from Bovine Liver

Isolation of enzymes and experiments on them require great effort and cost and are time-consuming. Therefore, it is important to extend the usability of the enzymes by immobilizing them. In this study our purpose was to immobilize the enzyme aldose reductase (AR) and to optimize the experimental conditions of the immobilized AR and compare them to those of free AR. AR was isolated from bovine liver and the enzyme immobilized in photographic gelatin by cross-linking with glutaraldehyde. Then the optimum conditions for free and immobilized AR in terms of pH, temperature, and storage were characterized by determining the enzyme activity. Following immobilization, the optimum pH and temperature levels for free AR, which were pH 7.0 and 60°C, slightly altered to pH 7.5 and 50°C. The enzyme activity of the immobilized AR was maintained at about 65% after reusing 15 times. Moreover, immobilized AR maintained 95% of its original activity after 20 days of storage at 4°C, while the retained activity of the free AR was 85% of the original. Our experiments indicated that the conditions that affect enzyme activity might alter following immobilization. Once the optimum experimental conditions are fixed, the immobilized AR can be stored and reused with efficiency higher than that of free AR. Moreover, this study provides an insight into the advantages of using immobilized AR in enzyme assays rather than free AR.