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

• Published in: Journal of agricultural and food chemistry 2011-05, Vol.59 (10), p.5636-5647
• Main Authors: Sørensen, Jesper, Palmer, David S, Qvist, Karsten Bruun, Schiøtt, Birgit
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Biological and medical sciences; camels; Camelus; Caseins - chemistry; Caseins - metabolism; Cattle; Cheese - analysis; cheeses; chymosin; Chymosin - chemistry; Chymosin - metabolism; cows; dairy protein; Food Chemistry/Biochemistry; Food industries; Fundamental and applied biological sciences. Psychology; kappa-casein; milk; Milk and cheese industries. Ice creams; Models, Molecular; molecular dynamics; Molecular Sequence Data; Peptide Fragments - chemistry; peptides; Sequence Alignment
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf104898w

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.