Editing Chymosin (section)

==Enzymatic reaction==
Chymosin is used to bring about the extensive [[Precipitation (chemistry)|precipitation]] and [[curd]] formation in [[cheese]]-making. The native substrate of chymosin is [[K-casein]] which is specifically [[Bond cleavage|cleaved]] at the [[peptide bond]] between amino acid residues 105 and 106, [[phenylalanine]] and [[methionine]].<ref name="Gilliland">{{cite book | vauthors = Gilliland GL, Oliva MT, Dill J | title = Structure and Function of the Aspartic Proteinases | chapter = Functional Implications of the Three-Dimensional Structure of Bovine Chymosin | series = Advances in Experimental Medicine and Biology | volume = 306 | pages = 23–37 | year = 1991 | pmid = 1812710 | doi = 10.1007/978-1-4684-6012-4_3 | isbn = 978-1-4684-6014-8 }}</ref> The resultant product is [[calcium phosphocaseinate]].{{Citation needed|date=August 2010}} When the specific linkage between the [[hydrophobic]] (para-casein) and [[hydrophilic]] (acidic [[glycopeptide]]) groups of [[casein]] is broken, the hydrophobic groups unite and form a [[Three-dimensional space|3D]] network that traps the aqueous phase of the milk.

Charge interactions between [[histidine]]s on the kappa-casein and [[glutamate]]s and [[aspartate]]s of chymosin initiate enzyme binding to the substrate.<ref name="Gilliland"/>  When chymosin is not binding substrate, a beta-hairpin, sometimes referred to as "the flap," can hydrogen bond with the active site, therefore covering it and not allowing further binding of substrate.<ref name="pmid9862200"/>