THE TRYPANOCIDAL CAPE BUFFALO SERUM-PROTEIN IS XANTHINE-OXIDASE

Plasma and serum from Cape buffalo (Syncerus caffer) kill bloodstream stages of all species of African trypanosomes in vitro, The trypanocid al serum component was isolated by sequential chromatography on hydrox ylapatite, protein A-G, Mono Q, and Superose 12. The purified trypanoc idal protein had a molecular mass of 150 kDa, and activity correlated with the presence of a 146-kDa polypeptide detected upon reducing sodi um dodecyl sulfate-polyacrylamide gel electrophoresis, Amino acid sequ ences of three peptide fragments of the 146-kDa reduced polypeptide, l igand affinity and immunoaffinity chromatography of the native protein , and sensitivity to pharmacological inhibitors, identified the trypan ocidal material as xanthine oxidase (EC 1.1.3.22), Trypanocidal activi ty resulted in the inhibition of trypanosome glycolysis and was due to H2O2 produced during catabolism of extracellular xanthine and hypoxan thine by the purine catabolic enzyme.