The turnover of bacterial luciferase is limited by a slow decomposition of the ternary enzyme-product complex of luciferase, FMN, and fatty acid.
Bacterial luciferase catalyzes the conversion of reduced flavin mononucleotide, O2, and fatty aldehyde to FMN, H2O, and fatty acid with light being emitted at a very low rate characterized by the decay of luminescence in single turnover flash assays. The present studies have now revealed that the decomposition of the ternary complex of luciferase with FMN and myristic acid occurs at a rate 10-15 times slower than the decay of luminescence and that functional luciferase is only regenerated after the release of flavin. In contrast, the rate of FMN dissociation and recovery of activity observed with a binary luciferase-FMN complex was more rapid indicating that release of fatty acid played the critical role in determining the rate of FMN dissociation from the ternary complex. Decomposition of the ternary complex was shown to occur by an ordered process involving the slow release of fatty acid followed by the more rapid release of flavin. The present results suggest that the rate-limiting step for the turnover of luciferase occurs subsequent to emission of light and would be the controlling step under conditions (e.g. in cells) with continuous light emission.
Li
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Department of Biochemistry, McGill University, Montreal, Quebec, Canada.
Meighen
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EA
D004795:Enzyme Stability; D004926:Escherichia coli; D005230:Fatty Acids, Nonesterified / Q000494:pharmacology; D005486:Flavin Mononucleotide / Q000378:metabolism; D007700:Kinetics; D008156:Luciferases / Q000378:metabolism*; D008163:Luminescent Measurements; D019814:Myristic Acid; D009227:Myristic Acids / Q000494:pharmacology; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism
D005230:Fatty Acids, Nonesterified; D009227:Myristic Acids; D011994:Recombinant Proteins; D019814:Myristic Acid; D005486:Flavin Mononucleotide; D008156:Luciferases