Rennin acts on milk protein and changes

Rennin, also known as chymosin, is a proteolytic enzyme and synthesized by chief cells in the stomach. Its role in digestion is to curdle or coagulate milk in the stomach. It acts on milk protein and changes casein into paracasein. If milk were not coagulated, it would rapidly flow through the stomach and miss the opportunity for initial digestion of its proteins.