Takeshi NAKAMURA
Toshio YANAGISAWA
Department of Parasitology, School of Medicine, Kitasato University, Sagamihara, Kanagawa 228, Japan.

Akiko TAKE-WATANABE
Section of Preventive Medicine, School of Medicine, Kitasato University, Sagamihara, Kanagawa 228, Japan.

Abstract
Enzyme activities has been observed in the plerocercoid of Spirometra erinaceieuropaei, the causative parasite of human sparganosis, that cleaves the actin of the worm itself. The protease present in 0.1 M NaCl extracts from acetone-treated larvae was partially purified and concentrated by ammonium sulfate fractionation. The resulting protease rapidly cleaved molecules of native actin and myosin from vertebrates, which are muscle structural proteins, at neutral pH. In contrast to this phenomenon, the protease was unable to cleave albumin and globulin, two serum components. The actin cleavage reaction was completely inhibited by the presence of leupeptin. It was, however, not inhibited by pepstatin, phenylmethanesulfonyl fluoride or EDTA. Based on these findings, cleavage of native muscle structural proteins were considered to be the result of action by enzyme resembling cysteinyl protease.