STRUCTURAL REQUIREMENTS FOR THE INDUCTION AND INHIBITION OF 2,3-DIHYDROXYBENZOIC ACID DECARBOXYLASE OF ASPERGILLUS-NIGER

2,3-Dihydroxybenzoic acid decarboxylase in Aspergillus niger was induced by many substrate analogs including salicylate and gentisate. Catechol, which is the product, induced the enzyme tenfold. The purified enzyme was competitively inhibited by many ortho substituted benzoic acids. The Ki values for salicylate, o-fluoro and o-chloro benzoic acids were 0.12 m M, 0.12 m M, and 0.13 mM respectively; these values were lower than the Km value for the substrate. As the size of the group in the ortho position increased, as in the case of bromo- and iodo-derivatives, there was an increase in their Ki values. The C-2 hydroxyl group was essential both for the induction and for interaction with the enzyme. The C-3 hydroxyl group was not necessary for induction or inhibition, but it might be essential for the catalysis. © 1990 Springer-Verlag New York Inc.