Dextran conjugated enzyme, effect

Our present approach in the preparation of new dextran-enzyme conjugates is initially to test the standard conditions. If such conditions do not give satisfactory results, either in terms of retention of activity or extent of conjugation, the effect of the three important parameters, pH, temperature and duration of reaction are then investigated to establish appropriate conditions for coupling. In some cases it has also been found useful to examine the effect of these variables on the stability characteristics and other properties of the resulting dextran-enzyme conjugates. 

Effect of Carbohydrate on Enzyme-Substrate Interaction. Since many of the enzymes we have conjugated with dextran have macromolecules as their natural substrates, we recognized that the conjugation process might result in unfavorable steric interactions that would impair the ability of the enzymes to interact with such substrates, in the same way that attached carbohydrate affects the susceptibility of the conjugated enzymes to proteolytic attack. We have therefore investigated the effect of carbohydrate on the interaction of conjugated enzymes with substrate. 

Miscellaneous. In addition to the effect of conjugation of a-amylase on its heat stability, stability in denaturants, and stability on cofactor removal, the attachment of dextran also results in improved stability of this acid-labile enzyme at pH values below about 5.0. Studies on the dependence of stability of Bacillus amyloliquefaaiens a-amylase on pH showed that the conjugated enzyme retained 20, 15 and 7% more activity at pH 3.5, 4.0 and 4.5 than did the native enzyme. 

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