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. Gelatinsubstrate 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-Iike proteinases.