Chymosin

Chymosin or rennin is an enzyme found in rennet. It is produced by ruminant animals in the lining of the abomasum. Chymosin is produced by gastric chief cells in infants to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. Bovine chymosin is now produced recombinantly in E. coli, Aspergillus niger var awamori, and K. lactis as alternative resource. The gene is found in humans (on chromosome 1), but it is not expressed.