Chymosin
（重定向自Rennin）
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Chymosin /ˈkaɪməsᵻn/ or rennin /ˈrɛnᵻn/ is a protease found in rennet. It is an aspartic endopeptidase belongs to MEROPS A1 family. It is produced by newborn ruminant animals in the lining of the fourth stomach to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. It is widely used in the production of cheese. Bovine chymosin is now produced recombinantly in E. coli, Aspergillus niger var awamori, and K. lactis as alternative resource.