ENZYMATIC COMBUSTION OF AROMATIC AND ALIPHATIC-COMPOUNDS BY MANGANESEPEROXIDASE FROM NEMATOLOMA-FROWARDII

The direct involvement of manganese peroxidase (MnP) in the mineraliza tion of natural and xenobiotic compounds was evaluated, A broad spectr um of aromatic substances were partially mineralized by the MnP system of the white rot fungus Nematoloma frowardii. The cell-free MnP syste m partially converted several aromatic compounds, including [U-C-14]pe ntachlorophenol ([U-C-14]PCP), [U-C-14]catechol, [U-C-14]tyrosine, [U- C-14] tryptophan, [4,5,9,10-C-14]pyrene, and [ring U-C-14]2-amino-4,6- dinitrotoluene ([C-14]2-AmDNT), to (CO2)-C-14.,, Mineralization was;as dependent on the ratio of MnP activity to concentration of reduced gl utathione (thiol-mediated oxidation), a finding which was demonstrated by using [C-14]2-AmDNT as an example., At [C-14]2-AmDNT concentration s ranging from 2 to 120 mu M, the amount of released (CO2)-C-14, was d irectly proportional to the concentration of [C-14]2-AmDNT. The format ion of highly polar products was also observed with [C-14]2-AmDNT and [U-C-14]PCP; these products were probably low-molecular-weight, carbox ylic acids, Among the aliphatic compounds tested, glyoxalate was miner alized to the greatest extent, Eighty-six percent of the (COOH)-C-14-g lyoxalate and 9% of the (CHO)-C-14-glyoxalate were converted to (CO2)- C-14,, indicating that decarboxylation reactions may be the final step in MnP-catalyzed mineralization, The extracellular enzymatic combusti on catalyzed by MnP could represent an important pathway for the forma tion of carbon dioxide from recalcitrant xenobiotic compounds and may also have general significance in the overall biodegradation of resist ant natural macromolecules, such as lignins and humic substances.