Pancreatic trypsin inhibitor. 1. Preparation and properties

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Abstract
Crystalline pancreatic trypsin inhibitor was obtained from industrial pancreas residues remaining after insulin extraction. Three separate prepns. yielded materials of similar composition but of slightly differing activities. The homogeneity of one prepn. was investigated by the specific property solubility test. The properties of the inhibitor were those of a basic peptide; it migrated during electrodialysis through cellophan to the cathode when the pH of the center was below 10. Elementary analysis was C, 47.6; H, 6.7; N, 16.5%. The molecular wt. was 9000 [plus or minus] 500. The amino acid composition was determined mostly by paper chromatography. Histidine was absent and there was only one methionine residue/ mol. of inhibitor. Cystine was determined amperometrically on unhydrolyzed inhibitor after electrolytic reduction in the presence of urea. End-group assay showed arginine to be the terminal amino acid. The inhibitor was slowly inactivated in alkaline soln. at room temp., but was stable in hot dilute acid.