Online Mendelian Inheritance in Man (OMIM)

Caseins are the major components of human milk and are the primary source of amino acids, calcium and phosphate for the suckling infant. The human caseins include alpha-S1- and beta-casein (115460), which are the substrates for protein kinase and precipitate in the presence of calcium (so-called calcium-sensitive caseins), and kappa-casein (601695), which prevents the precipitation of the other caseins by calcium through micelle formation (summary by Fujiwara et al., 1997).

Fujiwara et al. (1997) demonstrated that in the human the alpha-S1 beta, and kappa forms of casein are closely linked and arranged in that order, with about 10 kb between the first 2 and about 300 kb between the latter 2. By FISH, they mapped the casein gene family to chromosome 4q21.1.

Rijnkels et al. (1997) concluded that the human casein 'locus' comprises at least 4 casein genes: 3 genes encoding calcium-sensitive, casein-like genes and 1 kappa-like casein gene, in the order alpha-s1--beta--alpha-s2--kappa. The approximate size of the human casein gene locus is 350 kb.

Chen et al. (1995) suggested that the casein cluster is located within 700 kb of the albumin (103600) gene cluster on 4q13.

Milk casein can apparently be separated by urea starch electrophoresis into 3 regions, alpha, beta, and kappa casein. Alpha and beta variants of casein are present in the human population. Voglino and Ponzone (1972) postulated 2 biallelic systems. In Italy the frequency of the 2 alpha alleles was 0.908 and 0.092; 2 beta alleles had a frequency of 0.678 and 0.322.