Heparin Inhibition of Human Neutrophil and Eosinophil-Enriched Leukocyte Acid β-Glycerophosphatase

Abstract

Heparin inhibited acid β-glycerophosphatase (EC 3.1.3.2) from human blood leukocytes, eosinophil-enriched leukocytes, and neutrophils. The inhibition interfered in the hydrolysis of phosphorus from glycerophosphate, not in the formation or detection of colored complexes of phosphomolybdate in the second or color development step in two conventional assays. Heparin inhibited human hypereosinophilic syndrome leukocyte homogenate enzyme activity according to the equation: activity equals 0.946-0.087 In heparin (units/assay) when heparin was varied from 1 to 100 units per assay. At 100 units of heparin per assay, 51% of the original activity remained. Enzyme activity was less in neutrophils than in eosinophils; moreover, the inhibition of neutrophil homogenate by heparin was considerably less than that seen in the Eosinophil-enriched leukocyte preprations. In neutrophil homogenates containing 100 units of heparin per assay, 77.1% of activity without heparin was retained. When neutrophil lysates were utilized, less inhibition was observed e.g., at 1 unit of heparin per assay, 91.7% enzyme activity was retained and at 1000 units, 76.2%; here, activity equals 0.289-0.007 In heparin. The data allowed more precise consideration of the inhibition of acid β-glycerophosphatase by heparin, and, while confirming quantitatively the greater content of acid β-glycerophosphatase in eosinophil-enriched leukocyte preparations than in neutrophil preparations, provide experimental support for an acid β-glycerophosphatase in human eosinophils, which is different from that in human neutrophils. It is more highly susceptible to heparin inhibition than acid β-glycerophosphatase in human neutrophils from which it is apparently distinct.