CHARACTERIZATION OF PROTEINASES IN EXTRACTS OF ADULT HAEMONCHUS-CONTORTUS, THE OVINE ABOMASAL NEMATODE

The degradation of several protein substrates, including the blood pro teins haemoglobin, albumin and fibrinogen, by proteinases present in e xtracts of adult Haemonchus contortus was examined over a broad pH ran ge. These proteinases were further characterized on the basis of subst rate specificity, inhibitor sensitivity and molecular size by spectrop hotometric and substrate gel analysis. The majority of the proteinases capable of degrading the blood proteins tested were active at acidic pH and could be ascribed to the cysteine proteinase class. In addition , evidence is presented that these proteinases are differentially reco gnized and inhibited by immune sera and that parasites capable of with standing protective host immune responses exhibit modified expression of proteinases.