Non-Specific Effects of Exogenous Compounds on Bacterial Bioluminescent Enzymes: Fluorescence Study

A study of influence of exogenous (xenobiotic) molecules on enzymatic reactions provides a basis for prediction and interpretation of effects of toxic compounds on metabolic processes in complex organisms. A coupled system of two enzymatic reactions catalyzed by luciferase and NAD(P)H:FMN-oxidoreductase from luminous bacteria Photobacterium phosphoreum is considered as a simple model of a living organism. Three main mechanisms of xenobiotics' influence are: (1) change of electron-excited states population in a bioluminescent emitter; (2) change of rates of the coupled reactions; and (3) interactions with the enzymes. The paper mainly deals with the third case. The results of impacts of different molecular groups (fluorescent dyes, organic oxidizers, and haloid compounds) are summarized. Binding of the compounds with the enzymes is tracked through time-resolved fluorescence techniques. Results of an indirect fluorescent method for studying interactions of nonfluorescent compounds (quinones) with the enzymes are discussed. Correlations between physico-chemical characteristics of exogenous compounds (hydrophobicity or atomic weight of haloid substituents) and efficiency of their interactions with the enzymes are demonstrated.