Isolation and purification of bovine myeloperoxidase from neutrophil granules.

Bovine myeloperoxidase (MPO) was isolated and purified from neutrophil granules using protein extraction at pH 4 and gel filtration combined with fast protein liquid chromatography. The extracted protein was identified as MPO based on its absorption spectrum, amino acid composition, peroxidase activity and polypeptide structure. Bovine neutrophils contained three different forms of MPO (I, II and III). When subjected to sodium dodecyl sulphate polyacrylamide gel electrophoresis each of the three purified forms showed two distinct bands corresponding to heavy and light polypeptide chains of approximately 57,000 and 15,000 molecular radius. Amino acid analysis of the three forms showed that there was an overall similarity between them. Slight differences were found between MPO Form III and the other two forms. The three forms of bovine MPO were shown to differ in their specific enzyme activities in a luminol-dependent chemiluminescence assay. MPO Form III showed the highest enzyme activity. The amount recovered during purification of the respective MPO forms varied, with the recovery being highest for MPO I. Our findings suggest that there are intrinsic differences between the three forms of bovine MPO. In terms of their amino acid composition and molecular weight, the bovine MPO closely resembled human and canine MPO.