Pepsin in the toad Bufo marinus.

ABSTRACT

The macroscopic localization of pepsinogen in the upper gastrointestinal tract of the anuran Bufo marinus was studied by means of biochemical assay. The pH optimum of the anuran pepsin was determined to be 1.6. The effect of lowered ambient temperature on stored pepsinogen and proteolytic activity was studied. Both parameters were reduced. The results are extrapolated to speculate on the mechanisms of gastric brooding in gastric brooding frogs of the genus Rheobatrachus.