Abstract
A crude extract of Ascaris lumbricoides strongly inhibits pepsin and trypsin but not papain; the extract shows no proteolytic activity. An active trypsin inhibitor was isolated by fractional precipitation. It is not precipitated by trichloracetic acid and has the properties of a polypeptide.The inhibitor acts instantaneously on trypsin, exerting its maximum effect at neutral and acid reactions, with a minimum at pH 5. The effect of concentration suggests a reversible combination between enzyme and inhibitor. The inhibitor has no effect on papain, but stimulates peptic digestion.