title: Initial stage of cheese production: a molecular modeling study of bovine and camel chymosin complexed with peptides from the chymosin-sensitive region of κ-casein.
abstract: Bovine chymosin has long been the preferred enzyme used to coagulate cow's milk, in the initial stage of cheese production, during which it cleaves a specific bond in the milk protein κ-casein. Recently, camel chymosin has been shown to have a 70% higher clotting activity toward cow's milk and, moreover, to cleave κ-casein more selectively. Bovine chymosin, on the other hand, is a poor clotting agent toward camel's milk. This paper reports a molecular modeling study aimed at understanding this disparity, based on homology modeling and molecular dynamics simulations using peptide fragments of κ-casein from cow and camel in both bovine and camel chymosin. The results show that the complex between bovine chymosin and the fragment of camel κ-casein is indeed less stable in the binding pocket. The results also indicate that this in part may be due to charge repulsion between a lysine residue in bovine chymosin and an arginine residue in the P4 position of camel κ-casein.
authors.affiliation: The Center for Insoluble Protein Structures (inSPIN) and the Interdisciplinary Nanoscience Center (iNANO), Aarhus University, Aarhus C, Denmark.
authors.forename: Jesper
authors.initials: J
authors.lastname: Sørensen
authors.forename: David S
authors.initials: DS
authors.lastname: Palmer
authors.forename: Karsten Bruun
authors.initials: KB
authors.lastname: Qvist
authors.forename: Birgit
authors.initials: B
authors.lastname: Schiøtt
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002162:Camelus; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism; D002417:Cattle; D002611:Cheese / Q000032:analysis*; D012085:Chymosin / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry*; D016415:Sequence Alignment
chemical_list: D002364:Caseins; D010446:Peptide Fragments; D012085:Chymosin