AN ENZYME SYSTEM IN THE GASTRIC SECRETION CAPABLE OF REDUCING THE VISCOSITY OF NATIVE SOLUBLE CALF-SKIN COLLAGEN

Gastric juice from various animals contained an enzyme system capable of reducing the viscosity of a solution of native calf-skin collagen. These enzymes were confined in their action to the end-chains of collagen and could not be classified as collagenases. The end-chains contributed approx. 30% of the initial solution viscosity of collagen. Commercial preparations of pepsin (EC 3.4.4.1) differed in their ability to reduce the viscosity of collagen. Chromatographically homogeneous pepsin and three chromatographic subfractions (pepsins B, C and D) were demonstrated to have different actions on soluble collagen as indicated by viscosity changes. The individual pepsin enzymes had characteristic affinities for collagen and probably had different substrate specificities. The different actions of commercial pepsins on collagen could be accounted for by the presence of pepsin plus one or more of the more active subfractions. It was suggested that one sample of commercial crystalline pepsin and also human gastric juice contained a pepsin-like enzyme, other than any of the subfractions at present isolated, which was very much more active than any purified pepsin.