A 40 kDa cysteine protease was purified from the crude extract of adult worms of Gymnophalloides seoi by two consecutive steps: Sephacryl S-200 HR and DEAE-Sephacel chromatography. Enzyme activities were completely inhibited by cysteine protease inhibitors. L-trans-epoxysuccinylleucylamido (4-guanidino) butane (E-64) and iodoacetic acid, strongly suggesting that the purified enzyme belongs to the cysteine family of proteases. The enzyme was maximally active at pH 4.5 in 0.1 M of buffer, and its activity was greatly potentiated in the presence of 5 mM dithiothreitol. The protease degraded macromolecules with differential capabilities; it degraded extracellular matrix proteins, such as collagen and fibronectin, with a stronger activity against collagen than fibronectin. However, the enzyme digested hemoglobin and human immunoglobulins only slightly, leaving them nearly intact after an overnight reaction. Our results suggest that the cysteine protease of G. seoi adults is potentially significant in the nutrient uptake from the host intestine.
