Isolation and partial characterisation of a potentially pathogenic cysteine proteinase from adult Dictyocaulus viviparus

Dictyocaulus viviparus adult worms feed on pulmonary tissues and cause significant pathology in the bovine host. In this report, acidic extracts of these organisms were examined for cysteine proteinase activity. A soluble thiol-dependent proteinase with native molecular weight of ∼ 25 kDa was isolated and partially purified. This enzyme had maximal activity at acidic pH and showed inhibitor susceptibilities similar to the vertebrate acidic cysteine proteinases. When stored at 4°C, it was stable at pH 5.0 for at least 10 days and at pH 7.0 for at least 24 h. The D. viviparus cysteine proteinase was capable of degrading type I collagen and hemoglobin. It is suggested that this enzyme may be involved in the nutrition of this parasite and/or have the potential to contribute to bronchial pathology in cattle.