Pyrene is metabolized to bound residues by Penicillium janthinellum SFU403

We have previously shown that the filamentous fungus, Penicillium janthinel lum SFU403 (SFU403) oxidizes pyrene to pyrene 1,6- and 1,8-quinones and tha t the level of pyrenequinones (PQs) subsequently declines suggesting that P Qs are not terminal metabolites. The purpose of this study was to determine the fate of PQs in SFU403. First, we compared the fate of C-14-pyrene in S FU403 and a non-pyrene-oxidizing fungus, a Paecilomyces sp.. After 7 days o f incubation, more than 80% of the radioactivity was cell-associated in bot h fungi; however, while 90% of the C-14 could be extracted from the Paecilo myces sp. as unmetabolized pyrene, 65-80% of the bound radioactivity remain ed inextractable from SFU403. Further evidence that pyrene oxidation to PQs was required for irreversible binding was obtained by comparing the extent of C-14 bound to SFU403 when it was grown for 21 days under conditions tha t resulted in differing amounts of C-14-pyrene oxidation. The results showe d that approximate to 40% of the inextractable products were bound residues derived from pyrene metabolites. The balance (60%) could be attributed to strong sorption of unreacted pyrene. We used electron paramagnetic resonanc e spectroscopy and oxygen consumption studies to demonstrate that both NADP H and glutathione can reduce PQs by one electron to their corresponding sem iquinone anion radicals in vitro. These studies demonstrate that PQs are me tabolized by SFU403 to bound residues, possibly via semiquinone intermediat es.