The role of theSphingomonasspecies UG30 pentachlorophenol-4-monooxygenase inp-nitrophenol degradation

Abstract

Pentachlorophenol-4-monooxygenase is an aromatic flavoprotein monooxygenase which hydroxylates pentachlorophenol and a wide range of polyhalogenated phenols at their para position. The PCP-degrading Sphingomonas species UG30 was recently shown to mineralize p-nitrophenol. In this study, the UG30 pcpB gene encoding the pentachlorophenol-4-monooxygenase gene was cloned for use to study its potential role in p-nitrophenol degradation. The UG30 pcpB gene consists of 1614 bp with a predicted translational product of 538 amino acids and a molecular mass of 59,933 Da. The primary sequence of pentachlorophenol-4-monooxygenase contained a highly conserved FAD binding site at its N-terminus associated with a beta alpha beta fold. UG30 has been shown previously to convert p-nitrophenol to 4-nitrocatechol. We observed that pentachlorophenol-4-monooxygenase catalyzed the hydroxylation of 4-nitrocatechol to 1,2,4-benzenetriol. About 31.2% of the nitro substituent of 4-nitrocatechol (initial concentration of 200 microM) was cleaved to yield nitrite over 2 h, indicating that the enzyme may be involved in the second step of p-nitrophenol degradation. The enzyme also hydroxylated p-nitrophenol at the para position, but only to a very slight extent. Our results confirm that pentachlorophenol-4-monooxygenase is not the primary enzyme in the initial step of p-nitrophenol metabolism by UG30.

Induction of aromatic ring: cleavage dioxygenases in Stenotrophomonas maltophilia strain KB2 in cometabolic systems

“…As the compounds similar in structure to transformed nitroaromatics accelerate their degradation, for mononitrophenols degradation other phenolic compounds are frequently used as growth substrate (Cho et al 2000; Leung et al 1997, 1999; Wan et al 2007). …”

Characterization of Pentachlorophenol Degrading Bacterial Consortium from Chemostat

“…The aromatic ring is thus totally dechlorinated prior to ring cleavage (Wang et al 1998;Tartakovsky et al 1999Tartakovsky et al , 2001. Aerobic degradation of PCP has also been studied extensively and several bacterial strains capable of degradation have been reported such as Flavobacterium, Arthrobacter, Pseudomonas, and Sphingomonas (Edgehill and Finn 1983;Crawford and Mohn 1985;Saber and Crawford 1985;Xun and Orser 1991;Orser et al 1993;Edgehill 1994;Miethling and Karlson 1996;Chanama and Crawford 1997;Leung et al 1999;Thakur et al 2002;Yang et al 2006;Dams et al 2007).…”

Systems Biology Approach to Bioremediation of Nitroaromatics: Constraint-Based Analysis of 2,4,6-Trinitrotoluene Biotransformation by Escherichia coli

“…In the nitroaromatics bioremediation area, several effective gene manipulations have been reported [ 3 ]. For example, heterologous expression of pentachlorophenol from Sphingomonas strain UG30 (pcpB) to E. coli enabled the strain to degrade 4-nitrocatechol and p -nitrophenol concomitantly with nitrite release [ 76 ]. In another effort, heterologous expression in E. coli of recombinant plasmids from Enterobacter cloacae and P. pseudoalcaligenes JS45 carrying nitrobenzene reductase (nfs1) and nitrobenzene nitroreductase (nbzA), respectively, resulted in rapid conversion of nitrobenzene to aminophenol (64%) [ 77 ].…”