HYDROQUINONE DEGRADATION VIA REDUCTIVE DEHYDROXYLATION OF GENTISYL-COA BY A STRICTLY ANAEROBIC FERMENTING BACTERIUM

Anaerobic degradation of hydroquinone was studied with the fermenting bacterium strain HQGo1. The rate of hydroquinone degradation by dense cell suspensions was dramatically accelerated by addition of NaHCO3. D uring fermentation of hydroquinone in the presence of C-14-Na2CO3 benz oate was formed as a labelled product, indicating an initial ortho-car boxylation of hydroquinone to gentisate. Gentisate was activated to th e corresponding CoA-ester in a CoA ligase reaction at a specific activ ity of 0.15 mu mol x min(-1) x mg protein(-1) Gentisyl-CoA was reduced to benzoyl-CoA with reduced methyl viologen as electron donor by simu ltaneous reductive elimination of both the ortho and meta hydroxyl gro up. The specific activity of this novel gentisyl-CoA reductase was 17 nmol x min(-1) x mg protein(-1). Further degradation to acetate was ca talyzed by enzymes which occur also in other bacteria degrading aromat ic compounds via benzoyl-CoA.