Fasciola hepatica: a secreted cathepsin L-like proteinase cleaves host immunoglobulin.

Adult Fasciola hepatica secrete a cysteine proteinase capable of cleaving host IgG close to the papain cleaving site. The proteinase was separated by size permeation chromatography. Gelatin-substrate polyacrylamide gel electrophoresis analysis revealed that the proteinase migrates as 6 proteolytic bands in the apparent molecular size range 60-90 kDa. Based on pH profiles of activity, inhibition studies using diethylpyrocarbonate and the diazomethylketone Z-phe-ala-CHN2, and characterising the substrate specificity of the enzymes using fluorogenic peptide substrates we have shown that the 60-90-kDa proteinases are cathepsin L-like proteinases.