The Binding Ability of Bovine Milk Caseins to Mutagenic Heterocyclic Amines

Abstract

The binding ability of bovine milk caseins with mutagenic heterocyclic amines was investigated. Binding was determined with 2mg of casein and 20μg of heterocyclic amine in .40ml of pH 7.4, 50mM phosphate buffer, at 37°C, in a shaker for 10min. The unbound heterocyclic amine in protein-free ultrafiltrate was analyzed by HPLC. The binding ability of whole casein, αs-casein, β-casein, and κ-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-di-methyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole to αs-casein, β-casein, and κ-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-methyldipyridor[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.