Stability studies on the cathepsin L proteinase of the helminth parasite, Fasciola hepatica

Fasciola hepatica, the liver fluke, secretes a cathepsin L cysteine protein ase. The enzyme is active over the pH range 5-9 and is remarkably stable at 37 degrees C, pH 7.0, in contrast to mammalian cathepsin ts that are activ e in the acidic pH range and are inactivated within 15 min at neutral pH. T he liver fluke proteinase is also very tolerant of organic solvents, partic ularly dimethylformamide. However, it is completely inactivated by 1 mM Hg2 + and adversely affected by other heavy metals and divalent cations. Additi on of glycerol and EDTA enhanced the liver fluke enzyme's stability at 50 d egrees C, while glucose and glycerol protected the enzyme from inactivation by repeated freeze-thawing. The high stability of liver fluke cathepsin L suggests that it may have potential for use in bioindustrial applications. (C) 2000 Elsevier Science Inc. All rights reserved.