Observations on pancreatic rennet

Abstract

Pawlow and Parastschuk, 1 Vernon 2 as well as Delezenne 3 have called attention to the presence of rennet in the pancreatic secretion of experimental animals. Wohlgemuth 4 claims to have found it in human pancreatic secretion, but not without some difficulty. Notwithstanding these observations some doubt seems to exist in the minds of a number of investigators in this field. Textbooks on physiology do not class rennet with the other pancreatic ferments.

Fresh or well-preserved dried preparations of pancreatic extract ordinarily do not show any milk coagulating ferment. When solutions of such extracts are permitted to deteriorate the rennet function comes into evidence. While studying the pancreatic ferments I have found that the presence of rennet in extracts of this organ may be demonstrated constantly in a number of different ways.

1. Rennet may be liberated by heating a solution of the extract from 50 to 65°C. for a period of about 10-15 minutes; the most favorable temperature being 60°C. Flocculation usually occurs upon heating, but the ferment remains in solution.

2. The addition of suitable amounts of hydrochloric acids reveals the presence of rennet.

3. By treating solutions of pancreatic extract with colloidal iron and other precipitants such as uranium acetate, alcohol, sodium sulphate and others. Calcium chloride solution in concentration accomplishes the same result.

4. The addition of products of peptic digestion, such as those of gliadin or Witte's peptone, to solutions of pancreatic extract also liberate the rennet.

5. Serum of a rabbit immunized by intravenous injections of pancreatic extracts, when added to solutions of pancreatic extract, liberate the rennet.

Whatever method of activation is used, in every instance, the rennet itself remains in solution, and some substance is precipitated, which before precipitation conceals the presence of the rennet.