Alkaline phosphatase and 5'-nucleotide phosphodiesterase from bovine intestine are cross-reactive

Polyclonal antibodies to native alkaline phosphatase and to native 5'-nucleotide phosphodiesterase were found to strongly cross-react with both enzymes. The antibodies also cross-react with both denatured enzymes, with glycopeptides from 5'-nucleotide phosphodiesterase, and with the oligosaccharides remaining after Pronase E digestion of the phosphodiesterase. They do not cross-react with either enzyme after their oligosaccharides have been modified or removed by periodate or trifluoromethanesulfonic acid treatment. Antibodies to denatured 5'-nucleotide phosphodiesterase do not bind to the native phosphodiesterase or alkaline phosphatase but do cross-react with denatured alkaline phosphatase even after removal or modification of the carbohydrate moieties. These results suggest that antibodies to denatured 5'-nucleotide phosphodiesterase may recognize amino acid sequence homology between alkaline phosphatase and 5'-nucleotide phosphodiesterase. However, antibodies to native enzymes apparently recognize cross-reactive determinants of the native enzymes which are carbohydrate in nature. This is the first report of antimammalian alkaline phosphatase antibodies which recognize the carbohydrate moieties of the enzyme.