A stimulator of light emission of the luminous fungus Neonothopanus nambi

Biochemical mechanisms of bioluminescence of higher fungi remain poorly understood, and further research is needed. By now, in vitro experiments have shown that hispidin is a precursor of the substrate of basidiomycete luminescence reaction: NADPH-dependent hydroxylase transforms it into 3-hydroxyhispidin (luciferin), which is then oxidized by luciferase, generating light quanta. In the present study, the component stimulating luminescence of the fungus Neonothopanus nambi in vivo was detected in the aqueous extract after treatment of mycelium with β-glucosidase, and some of its properties were investigated. The addition of the extract to the luminous mycelium increased the level of its light emission from several times to 1.5 orders of magnitude or more. The light emission stimulator is a thermostable low-molecular-weight compound with an apparent molecular weight of 0.46 kDa. In the absorption spectrum of the aqueous sample of the stimulator, there are two major peaks in the short wavelength region at 205 and 260 nm and a shoulder in the 350–370 nm range. The stimulator is capable of blue fluorescence with the maximum light emission at 440 nm after excitation at 350–370 nm. The current study demonstrates that the component stimulating light emission is not the substrate (or substrate precursor) of the luminescence system of the fungus N. nambi. Having discovered the stimulator of fungal luminescence, we are faced with new research objectives to determine its structure and mechanism of stimulation.