Demonstration of chymosin (EC 3.4.23.4) in the stomach of newborn pig.

The stomach of newborn pig contains a proteinase that is immunologically closely related to calf chymosin (rennin) (EC 3.4.23.4.). None of the pepsins from the stomach of adult pig is present in the newborn pig. Pig chymosin has optimal general proteolytic activity around pH 3.5. The ratio of milk-clotting activity to general proteolytic activity is about 30--70 times higher than that of pyloric and fundic pepsins.