Nature of the Anti-anæmic Factor (Castle)

Abstract

IN a series of papers I have advanced the theory that the intrinsic factor of Castle might be identical with the enzyme aminopolypeptidase^1,2,3. In brief, the experiments reported in these papers demonstrated that intravenous injections of crystalline secretin provoked in cats a secretion from the mucous membrane of the distal part of the pyloric and the proximal part of the duodenal region, the part of the alimentary canal from which the intrinsic factor is considered to be secreted^4,5. The secretion contained a rather high concentration of aminopolypeptidase. In accordance with the results obtained by Castle, it was demonstrated that an enzymatic reaction (proteolysis) took place after incubating the secretion with a muscle extract. When preparing the enzyme from the hogs' pyloric mucosa, it was found that purified enzyme solutions apparently contained most of the intrinsic factor activity present in the mucous membrane. The intrinsic factor activity was estimated by allowing the purified enzyme solution to react with liver according to the methods outlined by Reimann⁶ and Sjögren⁷. At this stage of the investigation (1941) the aminopolypeptidase had been purified about ten times. Since then, the enzyme has been further purified, in all about a hundred times.