Digestion in Parasitic Nematodes. III. The Digestion of Proteins

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Abstract
Tryptic-like enzymes have been extracted from the intestines and intestinal contents of Ascarts lumbricoides and Strongylus edentatus. The action of these enzymes, in relation to hydrogen ion concentration, has been examined.The parasite trypsins resembled pancreatic trypsin in that the relative production of “free acid” and “formaldehyde acid” was similar, but though acting only on the alkaline side of the isoelectric points of the substrate proteins, optimum action on gelatin, blood-albumin and casein was obtained at pH 6·2.The amount of protease extracted from a given weight of S. edentatus tissue was far greater than that from a similar amount of A. lumbricoides. Thus Strongylus digested 4·9 to 8·3 times as much gelatin, 12·5 to 40·9 times as much casein and 2·5 to 5·2 times as much blood-albumin as Ascaris.Spectroscopic examination of the process of digestion of oxyhaemoglobin showed, first, the formation of reduced haemoglobin and then the formation of haematin. These changes took place most rapidly at higher hydrogen ion concentrations.