Chymosin

Chymosin
Crystal structure of bovine chymosin complex with the inhibitor CP-113972.
Identifiers
EC number	3.4.23.4
CAS number	9001-98-3
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Gene Ontology	AmiGO / EGO
Search PMC articles PubMed articles NCBI proteins

Chymosin [Precursor] (B.taurus or C.dromedarius)
X-ray analysis of calf chymosin
Identifiers
Symbol	Cym
Alt. symbols	CPC
Entrez	529879
PDB	4CMS
RefSeq	NP_851337.1
UniProt	Q9GK11

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 abomasum 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.

Chymosin is produced by ruminant animals in the lining of the abomasum. Chymosin is produced by gastric chief cells in young ruminants and some other newborn animals to curdle the milk they ingest, allowing a longer residence in the bowels and better absorption. Some other non-ruminant species, including pigs, cats, and seals, produce it.

One study claimed to find a chymosin-like enzyme in some human infants, but others have failed to replicate this finding. Humans have a pseudogene for chymosin that does not generate a protein, found on chromosome 1. Humans have other proteins to digest milk, such as pepsin and lipase.