Secretin Inactivating Enzyme in Liver.

Abstract

By means of isoelectric precipitation of a saline extract of dog''s liver, extraction of the precipitate with ethanol, and reprecipitation with acetone, a substance has been obtained which inactivates secretin and has the attributes of an enzyme. It''s activity is destroyed by heating in solution at 60-70[degree]C for 1 hour; dialysis of solutions for 22 to 168 hours resulted in no loss of activity; it is most active in the pH range 3-5 with an optimum of 4, and shows an initial linear relationship of activity to increasing 1) concentration and 2) incubation time. It acts on the non-specific protein substrates, hemoglobin and casein. This substance may be a cathepsin rather than a specific "secretinase ". Plasmin inactivated secretin at pH 7.0 and 7.4. Thus "secretinase " in blood, previously described by Green-gard et al, may be identified with plasmin as indicated by Rogers.