The acid phosphatases of bovine leucocytes, plasma and the milk of healthy and mastitic cows

Abstract

SummarySome of the acid phosphatase isozymes of bovine leucocytes and plasma have been separated and partly characterized. About 80% of the phosphatase activity of leucocytes at pH 4·9 was particle-bound and about 8% was extractable with Amberlite CG-50 ion exchange resin. This extractable enzyme existed as a single electrophoretic component with a mol. wt of about 42000 and with optimum activity at pH 5·8. Kmforp-nitrophenyl phosphate was 1·6 mM at pH 5·8 and 0·4 mM at pH 4·9. At pH 5·8 orthophosphate (K1= 1·5 mM) and pyrophosphate (Ki= 4·1 mM) were competitive inhibitors. The enzyme was also strongly inhibited by F−, Al3+, IO4−and S2032−. The enzyme which was not extractable with Amberlite was very heterogeneous with respect to molecular weight. At the pH optimum (4·9), Kmforp-nitrophenyl phosphate was 0·4 mM and orthophosphate (K1= 2·3 mM) and pyrophosphate (K1= 2·1 mM) were competitive inhibitors. Other inhibitors included F−, Al3+, Hg2+, IO4−and tartrate. The enzyme extracted from plasma by Amberlite CG-50 treatment had properties similar to that extracted from leucocytes. Normal bovine milk contained a single acid phosphatase, but milk from cows with mastitis showed 3 electrophoretic isozyme bands, one being the same as in normal milk; the 2 additional bands were of leucocyte origin.