Influence of gelatin solution and gel on bioluminescence of coupled enzymatic system of luminous bacteria NADH:FMN- oxidoreductase-luciferase was analyzed, thermostability and thermoinactivation of coupled enzyme system in gelatinous environment were studied. Activity of coupled enzyme system and kinetics of its thermoinactivation in gelatin with low concentration, that is insufficient for gel formation, and in gelatin with high concentration, that is sufficient for gel formation, was different. It was determined that thermoinactivation of coupled enzyme system has nonlinear nature and occurs with dissociative mechanism. It was showed that gel matrix of gelatin stabilizes enzymes. There was no effect of viscous environment originating by gelatin surroundings on the rate of enzymatic reactions.