Fluorene Oxidation In Vivo by Phanerochaete chrysosporium and In Vitro during Manganese Peroxidase-Dependent Lipid Peroxidation

Abstract

The oxidation of fluorene, a polycyclic hydrocarbon which is not a substrate for fungal lignin peroxidase, was studied in liquid cultures of Phanerochaete chrysosporium and in vitro with P. chrysosporium extracellular enzymes. Intact fungal cultures metabolized fluorene to 9-hydroxyfluorene via 9-fluorenone. Some conversion to more-polar products was also observed. Oxidation of fluorene to 9-fluorenone was also obtained in vitro in a system that contained manganese(II), unsaturated fatty acid, and either crude P. chrysosporium peroxidases or purified recombinant manganese peroxidase. The oxidation of fluorene in vitro was inhibited by the free-radical scavenger butylated hydroxytoluene but not by the lignin peroxidase inhibitor NaVO 3. Manganese(III)-malonic acid complexes could not oxidize fluorene. These results indicate that fluorene oxidation in vitro was a consequence of lipid peroxidation mediated by P. chrysosporium manganese peroxidase. The rates of fluorene and diphenylmethane disappearance in vitro were significantly faster than those of true polycyclic aromatic hydrocarbons or fluoranthenes, whose rates of disappearance were ionization potential dependent. This result indicates that the initial oxidation of fluorene proceeds by mechanisms other than electron abstraction and that benzylic hydrogen abstraction is probably the route for oxidation.

Lignin peroxidase functionalities and prospective applications

“…Nonetheless, MnP also possesses the capability to oxidize or cleave non-phenolic structures with the contributions of mediators including thiyl or lipid radicals (Abdel- Hamid, Solbiati, & Cann, 2013;Reddy, Sridhar, & Gold, 2003). Moreso, the ability of MnP to oxidize and depolymerize natural and synthetic lignin and as well, recalcitrant compounds has been reported (Bogan, Lamar, & Hammel, 1996;Dehorter & Blondeau, 1993;Hofrichter, 2002;Hofrichter, Steffen, & Hatakka, 2001;Hofrichter, Ullrich, Pecyna, Liers, & Lundell, 2010). MnPs possess two or three residues corresponding to Glu-35, Glu-39 and Asp-175 of Phanerochaete chrysosporium MnP 1 that binds Mn (Floudas et al, 2012;.…”

Formation of acyl radical in lipid peroxidation of linoleic acid by manganese-dependent peroxidase from Ceriporiopsis subvermispora and Bjerkandera adusta

“…The decrease in O 2 concentration in the reactions with oleic acid was less than 0.1 nmol´min 21 . It has been reported that fluorene was decomposed by MnP, Mn(II) and oleate, but the peroxidation started after a lag of 10±20 h [4]. Therefore, the presence of 1,4-pentadienyl moiety is not a prerequisite for MnP-dependent lipid peroxidation but the low dissociation energy of bis-allylic hydrogen (75±80 kCal´mol 21 ) compared with that of allylic hydrogen (88 kCal´mol 21 ) [28] greatly facilitates the induction of peroxidation as is obvious from the reaction rate between linoleic and oleic acid.…”

Antifungal activity of polycyclic aromatic hydrocarbons against Ligninolytic fungi

“…Ovaj početni izvještaj stimulirao je mnoge druge istraživače da pokažu da je lignin degradacioni sistem P. chrysosporium koji uključuje lignin peroksidazu (LiP) i mangan peroksidazu (MnP) značajan u razgradnji PAH--ova [6]. Za izolovane forme LiP i MnP također, bilo je pokazano da su pogodne za oksidaciju antracena, pirena, fluorena i benzo[a]pirena do odgovarajućih hinona [7][8][9]. Lignin, skupa sa celulozom i hemicelulozom, glavna je komponenta drvnog materijala i najobimnija forma aromatičnog ugljenika u biosferi.…”