Abstract
The interaction of human hepatic and intestinal alkaline phosphatase (EC 3.1. 3.1) with 17 amino acids or its derivatives was studied.
Of these. homogentisate was a potent inhibitor for both alkaline phosphatases. The pH profile for the enzymes with and without homogentisate was similar, but the enzyme·homogentisate complex showed a marked heat-lability at higher temperature.
According to the results of S/v against S plots, the mechanism of homogentisate inhibition for the intestinal enzyme was uncompetitive type and the Ki value was found to be 1mM.
To investigate the binding sites of homogentisate, bismuth and L-phenylanine on the intestinal enzyme molecule, the effect of homogentisate on the enzyme activity with and without L-phenylalanine or bismuth was studied. From the results of kinetic analysis, the L-phenylalanine and homogentisate binding sites is apparently independent of each other, while the sites for bismuth and homogentisate binding are presumed to be proximal to one another.
