[ Casein, Kappa_Casein, Alpha_Casein, Beta_Casein ]
Phosphoproteins which are predominant component of mammalian milk.
Caseins make up about 80% of the proteins in bovine milk and between 20% and 45% of the protein component of human milk. Caseins interact with calcium phosphate to form micelles, which maintain the high calcium phosphate concentration. Calcium phosphate is required by newborns for the mineralisation of calcified tissues.
Caseins are a major component of cheese and are widely used in the food industries as an additive. They have been implicated in food allergies, as well as having a possible causal link to autism. Focus has centred on differences between the A1 and A2 beta-casein types. A1 is the predominant type in commercially produced milk, while A2 is only prevalent in France.
Biochemically, there are four classifications of caseins: kappa, alpha S1, alpha S2 and beta.
Beta_casein A1 and A2 are genetic variants that differ only by one amino acid at position 67 of the amino acid chain. With A1 beta_casein, a histidine occurs at that position. With A2 beta_casein that position is occupied by proline.