A Chymotrypsin Inhibitor From the Parasitic Nematode, Oesophagostomum radiatum

Abstract

An inhibitor of oc-chymotrypsin was isolated from O. radiatum by affinity chromatography, as well as by ion-exchange and molecular sieve chromatography. The inhibitor was associated with the cuticle or musculature of the parasite. It completely inhibited the esterolytic activity of chymotrypsin. Molecular sieve chromatography gave an apparent molecular weight of 9700 for the inhibitor alone and 32000 for the complex with chymotrypsin. This suggests reaction in a 1: 1 molar ratio. The inhibitor reacted with diisopropyl phosphoryl-chymotrypsin weakly, if at all.Measurement of the dissociation constants for the enzyme-inhibitor complexes gave values of 2·2 X 10-9 M for the product of affinity chromatography but less than 2 x 10-10 M for all other preparations. Possible explanations of this are discussed.

A trypsin and chymotrypsin inhibitor from the metacestodes ofTaenia pisiformis

“…The proteolytic enzyme inhibitors studied and purified so far from parasitic helminths have been shown to be either proteins or protein-carbohydrate complexes with molecular weights ranging from 4650 to 20000 (Vogel et al 1966;Kassell, 1970;Ansari et al 1976;Willadsen, 1977;Matskasi & Nemeth, 1979). The protease inhibitor of larval T. pisiformis is probably a polypeptide having a mol.…”

“…Most of the present knowledge of their properties and function have been derived from experiments on Ascaris suum (Peanasky & LaskowsM, 1960;Peanasky & Szucs, 1964;Rola & Pudles, 1966;Pudles, Rola & Matida, 1967;Kucich & Peanasky, 1970;Kassell, 1970). However, the inhibitors of other species have also been investigated in some detail (Keninya, 1971;Ansari, Khan & Ghatak, 1976;Willadsen, 1977).…”