Characterization of leucocyte alkaline phosphatase in normal subjects and under different physiological and pathological conditions.

Leucocyte alkaline phosphatase activity was determined in both cell homogenates and cell extracts. Leucocytes were obtained from normal controls, pregnant females, and patients with various haematological disorders. Enzyme activity presented in terms of phosphorus per minute per 10 neutrophils was more in agreement with the reported cytochemical data in both normal and pathological cases, than the values expressed in terms of phosphorus per minute per 10 leucocytes or per protein. This was explained by the possible low enzyme activity of lymphocytes included in the latter. Cases of acute and chronic granulocytic leukaemias showed very low activity compared to normal ̂ irrespective of the method of presentation of activity. Characterization of leucocyte alkaline phosphatase isoenzyme in normal subjects, using substrate specificities and selective inhibition tests, showed that it is largely similar to that of liver, bone, kidney and spleen, but differs markedly from those of the intestine and placenta. In this respect, the leucocyte alkaline phosphatase in pathological cases showed no variation from normal, except in cases of acute and chronic granulocytic leukaemias and pregnancy, where the leucocyte alkaline phosphatase enzyme showed a tendency to be heat resistant. In addition, the enzyme from acute gramdocytic leukaemia eases showed ä higher affinity for -naphthylphosphate, o-carboxyphenylphosphate, and adenosine S'-monophosphate.