An immunological determination of specific activities of enzymes: its use in quantification of cross reactivity between enzymes of different origins.

An immunological method is presented which enables the determination of the specific activity of a pure enzyme without its extensive purification. The method consists essentially in the specific fixation of immunologically related enzymes to an immunoadsorbent containing specific antibodies raised against the wild-type form of the enzyme. We applied this method to determine the specific activity of plasmid-coded beta-galactosidases and to quantify the extent of cross-reaction between these enzymes and Escherichia coli beta-galactosidase.