Liver- and placenta-like alkaline phosphatases (EC 3.1.3.1) isoenzymes in normal human neutrophils

Alkaline phosphatase (AP) has been characterized in the neutrophil polymorphonuclear leukocytes (PMN) from 14 healthy adults. The biochemical properties of the isoenzymes were analyzed by the following methods: enzyme assays, slab gel electrophoresis, thermostability, inhibition pattern using four chemical inhibitors, and immunological specificity. In normal PMNs, two types of AP have been found: a thermolabile isoenzyme identical to the liver/bone/kidney type and a thermostable isoenzyme with respect to its electrophoretic properties, its level of thermostability, its immunological specificity, the thermostable isoenzyme resembles the placental form more closely than the intestinal form. These results are consistent with the proposal that granulocyte AP is a heterogeneous enzyme. Two enzyme forms appear to be expressed in this blood cell.