The localization and some properties of the acetylsalicylic acid O-deacetylases of Ascaris lumbricoides var suum and Moniezia expansa.

1. Enzymes hydrolysing acetylsalicylic acid were found in the cytosol of the cestode, Moniezia expansa, and in the cytosol of the intestinal epithelial cells and cytosol of the reproductive tract of the nematode, Ascaris lumbricoides var suum. 2. Enzymes hydrolysing 2-naphthyl acetate and 4-methylumbelliferyl acetate were found throughout the proglottid of the cestode and in the reproductive tract, intestine, mesenchyme fluid and cuticle of the nematode. These enzymes had mol. wt. of 30 000-300 000 whereas those hydrolysing acetylsalicylic acid in both species had mol. wt. of about 87 000. 3. The acetylsalicylic acid hydrolases from both helminths showed pH optima of about 7.0, and activity was enhanced by Ca2+ and low-mol. wt. thiols. Cu2+, Cd2+, Hg2+, Zn2+, La3+, F- and EDTA at 1 mM inhibited activity. N-Ethylmaleimide, p-chloromercuribenzoate, haloxon and paraoxon also inhibited hydrolase activity.