Purification and properties of pentachlorophenol hydroxylase, a flavoprotein from Flavobacterium sp. strain ATCC 39723

Abstract

A pentachlorophenol (PCP) hydroxylase which catalyzed the conversion of PCP to 2,3,5,6-tetrachlorohydroquinone and released iodide from triiodophenol in the presence of NADPH and oxygen was identified. The enzyme was purified by protamine sulfate precipitation, ammonium sulfate precipitation, hydrophobic chromatography, anion-exchange chromatography, gel filtration chromatography, and crystallization. The enzyme was a monomer with a molecular weight of 63,000. Under certain conditions, dimer and multimer conformations were also observed. The pI of the enzyme was pH 4.3. The optimal conditions for activity were a pH of 7.5 to 8.5 and a temperature of 40 degrees C. Each enzyme molecule contained one flavin adenine dinucleotide molecule. The Km for PCP was 30 microM and the Vmax was 16 mumol/min/mg of protein. The enzymatic reaction required 2 mol of NADPH per mol of halogenated substrate. On the basis of the data we present, it is likely that PCP hydroxylase is a flavoprotein monooxygenase. The addition of flavins to the reaction mixture did not stimulate the enzymatic reaction; however, we identified the photodegradation of triiodophenol and tribromophenol, but not PCP, by flavin mononucleotide or riboflavin and light.