Incubation with neuraminidase and affinity electrophoresis with wheat-germ lectin compared for separating and quantifying alkaline phosphatase isoenzymes in plasma.

Of 98 patients' specimens examined for alkaline phosphatase (EC 3.1.3.1) isoenzymes by electrophoresis on cellulose acetate membrane after incubation with neuraminidase, 50 showed only a single liver or bone isoenzyme staining band; in 15 of these, the tissue origin of the fraction could not be accurately identified from its electrophoretic location. In the remaining 48 specimens, both liver and bone fractions were identifiable, but in only 25 of these was the electrophoretic resolution sufficient to yield separate peaks on densitometry. In contrast, both liver and bone alkaline phosphatase isoenzymes were identified in 95 of the 98 specimens by affinity electrophoresis involving wheat-germ lectin, the detection of both fractions being in agreement with the results of sequential heat inactivation. The tissue origin of the enzyme bands was readily ascertainable from their consistent electrophoretic location in this medium, and in 89 of the specimens the isoenzyme fractions could be resolved into separate peaks on densitometry. We conclude that resolution of liver and bone alkaline phosphatase by incubation with neuraminidase followed by cellulose acetate electrophoresis is greatly inferior to that obtained by wheat-germ lectin affinity electrophoresis.