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.