The cytochrome P450 system is involved in the light emission of higher fungi

Abstract

The present study reports experimental data that suggest the participation of the cytochrome P450 system in light emission by higher fungi. The luminous mycelia of the basidiomycetes Neonothopanus nambi, Armillaria borealis, Panellus stipticus, and Mycena citricolor were used to prepare “cold” extracts, which contained luminescent enzyme systems responsible for the in vitro luminescence of the extracts. A “hot” extract from the mycelium of the nonluminous higher fungus Pholiota squarrosa was used as a substrate for the luminescent reaction. The conditions for preparing “cold” extracts (treatment of mycelial biomass with ultrasound and clarification of homogenates by centrifugation at 40000g) indicate the presence of membrane structures in them, microsomes, in particular, which are formed during ultrasonic destruction of the endoplasmic reticulum. In samples of the extracts treated with sodium dithionite and CO, differential spectroscopy revealed two absorption peaks, at 410 and 450 nm, which indicates the presence of cytochromes b5 and P450 in them. The luminescence of extracts is stimulated by reduced pyridine nucleotides, but it has been found that the addition of NADPH leads to a higher level of luminescence compared to NADH. The addition of NADPH results in the Vmax values of light emission higher by a factor of almost 2 and the apparent Km values lower by a factor of 2 compared to the addition of NADH. It has been shown that the addition of hydrogen peroxide substantially increases the luminescence intensity of extracts activated by NADPH and the reaction substrate. It has been found that fluconazole additives considerably inhibit the light emission of extracts when they are activated by NADPH and the reaction substrate. The results obtained in this study suggest that the mechanism of luminescence of higher fungi may involve the cytochrome P450 system associated with endoplasmic reticulum membranes, involving in the process the electron transport enzyme systems. In that case, cytochrome P450 carries out the hydroxylation of hispidin, the precursor of the substrate of the luminescence reaction, with the formation of luciferin, and catalyzes its oxidation in the presence of reactive oxygen species (hydrogen peroxide, in particular) with the emission of visible light quanta.