The Binding Ability of Bovine Milk Caseins to Mutagenic Heterocyclic Amines

Open Access
Publisher Website
Google Scholar
Abstract
The binding ability of bovine milk caseins with mutagenic heterocyclic amines was investigated. Binding was determined with 2 mg of casein and 20 micrograms of heterocyclic amine in .40 ml of pH 7.4, 50 mM phosphate buffer, at 37 degrees C, in a shaker for 10 min. The unbound heterocyclic amine in protein-free ultrafiltrate was analyzed by HPLC. The binding ability of whole casein, alpha s-casein, beta-casein, and kappa-casein, respectively, was 90.08, 83.06, 90.92, and 96.70% with 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole; 85.48, 51.54, 63.62, and 82.71% with 3-amino-1-methyl-5H-pyrido[4,3-b]indole; and 87.03, 59.77, 97.04, and 88.30% with 2-amino-6-methyldipyrido[1,2-a:3',2'-d]-imidazole. Higher binding of 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole to alpha s-casein, beta-casein, and kappa-casein was observed at pH above 7.4, and the binding was inhibited at pH below 6.5. The maximum binding of 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole to these caseins was at pH 6.6 and 7.4. The binding was inhibited at alkaline pH above 8.5 and acidic pH below 6.5.