Aromatic biosynthesis in higher plants. 3. Preparation and properties of dehydroquinase

Abstract

An enzyme catalysing the interconversion of dehydroquinic acid and dehydroshikimic acid was extracted from cauliflower buds and purified 7-6-fold by ammonium sulphate fractionation. The enzyme was found to be active over a broad range of pH, with no marked peak between pH 7.0 and 9.0. The Michaelis constant for dehydroquinic acid at pH 7-4 was 61 [mu]M. The enzyme did not catalyse the dehydration of malate or citrate. No inhibition was observed by sulphydryl reagents or by compounds related in structure to the natural substrates. There appeared to be no dialysable cofactor.