Granulocyte alkaline phosphatase. Studies of purified enzymes from normal subjects and patients with polycythemia vera

Abstract

To characterize the biological changes which result in increased granulocyte alkaline p-nitrophenyl phosphatase activity in patients with polycythemia vera, the enzyme was purified from granule fractions of sucrose homogenates made from dextran-sedimented leukocytes of normal subjects and patients with polycythemia vera. Polycythemic blood yielded 3-10 times as much granulocyte alkaline phosphatase per 10(9) leukocytes as did normal blood. Sodium dodecyl sulfate extracts of granules were purified by DEAE-cellulose chromatography and sucrose gradient centrifugation to apparent homogeneity as judged by polycarylamide disk gel electrophoresis. Granulocyte alkaline phosphatase from normal subjects was purified 6910-fold with a 60% yield and a specific activity of 47 U/mg. Granulocyte alkaline phosphatase from polycythemic patients was purified 1.166-fold with a 50% yield and a specific activity of 70 U/mg. The two enzymes did not differ in molecular weight; both appeared to be about 160,000 daltons by sucrose gradient centrifugation. Both appeared to be zinc metalloenzymes, in that they were specifically inhibited by o-phenanthroline. Their elution requirements when adsorbed to DEAE-cellulose suggested they were lipoproteins although the content of phosphorus was below the threshold of detection. The identity of the two enzymes was suggested by immunological studies in which antibody prepared against purified polycythemia vera enzyme gave a precipitation reaction of identity with another polycythemia vera enzyme and two pools of normal enzyme. It is possible to account for the difference in alkaline phosphatase activity between the granulocytes of patients with polycythemia vera and normal subjects by differences in the quantity of enzyme synthesized.