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Excystment of Paragonimus westermani Metacercariae by Endogenous Cysteine Protease
Young-Bae Chung, Yoon Kong, Il-Jung Joo, Seung-Yull Cho and Shin-Yong Kang
The Journal of Parasitology
Vol. 81, No. 2 (Apr., 1995), pp. 137-142
Stable URL: http://www.jstor.org/stable/3283911
Page Count: 6
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To infect definitive or paratenic hosts, metacercariae of Paragonimus westermani should excyst in the host intestine. Optimum conditions for the excystment have been known to be pH 8-9 and a temperature of 40 C. Under these conditions, excystment of P. westermani metacercariae was accelerated in the presence of 1 mM dithiothreitol (DTT). The DTT acceleration was antagonized dose-dependently by cysteine protease inhibitors of L-trans-epoxysuccinylleucylamido(4-guanidino)butane (E-64, 2-20 µM) or leupeptin (0.1-1 mM), suggesting that certain cysteine proteases of the metacercaria are involved in excystment. Protease activities were detected in excretory-secretory products (ESP) of newly excysted metacercariae. Two distinct proteases were purified by DEAE anion-exchange chromatography of the ESP. While a 27-kDa protease exhibited endodipeptidolytic activity at pH 5-8.5 and remained stable at neutral pH for 3 days, the 28-kDa enzyme was stable at pH 5-7.5, with lower activity at pH 8.5. Both proteases hydrolyzed collagen, fibronectin, and myosin within 1 hr at pH 8. These results suggest that cysteine proteases secreted by P. westermani metacercariae modulate excystment.
The Journal of Parasitology © 1995 The American Society of Parasitologists