Characterization of alkaline phosphatase in polymorphonuclear neutrophils from normal sheep

This paper is an attempt to the analysis of the main biochemical characteristics of alkaline phosphatase from sheep polymorphonuclear neutrophils. Ten male adult Romanoff X Berrichon sheep were studied. Alkaline phosphatase was analyzed from cell homogenates, after extraction and solubilization steps. The Vmax and Km values for 4-nitrophenylphosphate at pH = 9.80 were 347.3 +/- 34 IU/ml and 0.7 +/- 0.18 mmol/l, respectively. The pH optimum was 9.80 with 4-nitrophenylphosphate. L-Homoarginine and EDTA, but not L-phenylalanine, inhibited the enzyme. Magnesium above a concentration of 0.5 mmol/l has shown a protective effect against inhibition by 115, 156 and 250 mmol/l urea (final concentration). Sheep neutrophil alkaline phosphatase was found to be very heat-labile. Polyacrylamide gel electrophoresis indicated a single band of activity with a relative mobility similar to that of the slow component of bone and liver isozymes. It is suggested from the above results that sheep neutrophil alkaline phosphatase shares several biochemical properties similar to those of hepatic bone tissue isozyme.