Phenol Hydroxylase

Phenol hydroxylase is the first aromatic hydroxylase found in and purified from an eukaryote, the strictly aerobic soil yeast Trichosporon cutaneum. The tyrosyl reagent 4-nitrobenzene sulfonyl fluoride caused inhibition of the overall reaction of phenol hydroxylase. Phenol hydroxylase is coinduced with the whole metabolic sequence for phenol utilization, including active transport of phenol and the six consecutive enzymes transforming phenol to succinate and acetyl-CoA. Uncoupling of oxygen reduction from hydroxylation is observed with ali external aromatic hydroxylases. The profound conformational changes upon binding of phenolic substrates to aromatic hydroxylases and the concomitant increase of the rate of their flavin adenine dinucleotide (FAD) reduction by NADPH raise the question of a possible effect on the FAD redox potential. Hydroxylation of phenols is carried out by a completely different class of ubiquitous enzymes, designated by the vague terni "phenol oxidases". The enzymes contain copper instead of flavin at their redox active centers.