HUMAN TRYPSIN . ISOLATION AND PHYSICAL-CHEMICAL CHARACTERIZATION

The purification of human trypsin from activated extracts of human pancreas has been accomplished by a combination of salt fractionation, gel filtration on Sephadex G-75, and ion-exchange chromatography on SE-Sephadex C-25. The preparation was homogeneous by gel electrophoresis at pH 2.9 with a mobility comparable with bovine trypsin. At pH 4.3, disc electrophoresis indicated slight heterogeneity, although no other sharp bands could be detected. It is estimated that the purity of this preparation is greater than 95 %. Ultracentrifuge studies indicated a single component with a molecular weight of 22,900. The amino acid composition of this molecule indicates it to be similar to other mammalian trypsins; however, only four disulfide bonds are possible, as compared with six for the other mammalian species, and only one methionine residue is present. Human trypsin is inhibited by L-l-toslyamido-2-phenylethyl chloromethyl ketone and diisopropylphosphorofluoridate but not by soybean trypsin inhibitor or by ovomucoid. The absence of inhibition by these macromolecular inhibitors may be related to a difference in tertiary structure of the human enzyme as compared with other trypsins. This difference may be related to the decrease in disulfide bonds. © 1969, American Chemical Society. All rights reserved.