Properties of alkaline-phosphatase fractions separated by starch-gel electrophoresis.

The availability of refined techniques for the resolution of protein mixtures, e.g. chromatography on substituted cellulose ion-exchangers and zone electrophoresis on a variety of supporting media, has resulted in the separation of several enzymes that had previously been regarded as single entities into a number of active components (see Wr6blewski, 1961). These enzyme fractions, which catalyse similar reactions and have similar (but not necessarily identical) substrate specificities, but which differ in chemical, electrophoretic or immunological properties, have been termed isoenzymes. Starch-gel electrophoresis (Smithies, 1955), which combines electrophoretic separation with a molecular sieving effect, has proved particularly effective in resolving isoenzyme mixtures, and the heterogeneity of alkaline phosphatases from several human organs has been demonstrated in this way (Boyer, 1961). Moss, Campbell, Anagnostou-Kakaras & King (1961) reported the Michaelis constants, Ki, of the major fractions of alkaline-phosphatase activity from human liver, bone, kidney and small intestine after starch-gel electrophoresis. One or more minor phosphatase components are present after electrophoresis of extracts of each of these tissues, and the Km values of these have now been determined. Certain other properties of the alkaline-phosphatase fractions from these organs are also reported. A preliminary account of part of this work has been published (Moss & King, 1962).