INHIBITION OF RAT-LIVER ARYL SULFOTRANSFERASE BY THE FOOD ADDITIVE VANILLIN

The kinetics of the sulphate conjugation reaction catalysed by rat liver aryl sulphotransferase were determined with the substrates phenol, dopamine, p-nitrophenol and vanillin. Vanillin was assessed for its potential to inhibit the sulphation of the other substrates. It was found to be a potent inhibitor of all three substrates. The pattern of inhibition was consistent with a partial non-competitive or a mixed-type inhibition system. It is possible that this apparent non-competitive inhibition results from preferential inhibition of one enzyme in a two-enzyme system, depletion of co-substrate by vanillin or from a true non-competitive action where some functional component of vanillin, such as the carbonyl group, interacts independently with a distinct site of the enzyme.