An enzyme produced in the stomach that coagulates milk. It is secreted by the gastric glands in an inactive form, prorennin, which is activated by hydrochloric acid. Rennin converts caseinogen (milk protein) into insoluble casein in the presence of calcium ions. This insures that the milk remains in the stomach, exposed to protein-digesting enzymes, for as long as possible. Rennin is present in the largest amounts in the stomachs of young mammals.
The milk-coagulating enzyme produced by the lining of the stomach. Rennin converts milk protein into insoluble casein, thus ensuring that milk stays in the stomach for some time, during which it can be digested by various enzymes before passing into the small intestine.