Inhibition of human alkaline phosphatase isoenzymes by the affinity reagent reactive yellow 13.

The dye Reactive Yellow 13, an affinity reagent for intestinal alkaline phosphatase, inhibits intestinal and other human alkaline phosphatases in solution. The inhibition depends markedly on the presence of a phosphate acceptor such as diethanolamine. The dye is an uncompetitive inhibitor with respect to both substrate and phosphate acceptor in the case of non-intestinal phosphatases. However, in the case of intestinal alkaline phosphatase, the inhibition is noncompetitive with respect to the substrate and competitive with respect to the phosphate acceptor. These observations account for the specific binding of intestinal phosphatase when the dye is used as a ligand in affinity chromatography.