The functioning of NAD(P)H:FMN‑oxidoreductase (Red) from Vibrio fischeri under conditions of macromolecular crowding (MMC) simulated in vitro by adding biopolymers (starch and gelatin) was studied. The dissociation rate constants and the activation energies of dissociation of Red to the subunits were calculated, and the process of denaturation of Red was analyzed. It is shown that the functioning of Red both under conditions of MMC and in diluted solutions is the same. This result refutes the common belief that the native conformation of enzymes in vivo is stabilized due to MMC as compared to the in vitro conditions.