ANALYSIS OF THE RATIO OF QUANTUM YIELD AND FATTY ACID FORMATION OF PHOTOBACTERIUM LEIOGNATHI BIOLUMINESCENCE

The ratio of quantum yield and fatty acid produced in a bioluminescent reaction catalyzed by the luciferase of Photobacterium leiognathi with tetradecanal and FMN chemically reduced by dithiotreitol in the absence and presence of organic solvents|acetone and dimethyl sulfoxide (DMSO) has been studied. In the absence of organic solvents the light per a molecule of produced myristic acid is 0.21 quantum. Addition of organic solvents the ratio of the light product and fatty acid shifts towards considerable increase of myristic acid production. With addition of 1{6 vol.% of DMSO and 0.15 vol.% of acetone the quantum yield was 0.13{0.07 and 0.04 quanta of light per a molecule of myristic acid, respectively. Bacterial luciferase is a avin monooxygenase catalyzing the oxidation reaction of long-chain aliphatic aldehyde (RCOH) to a respective fatty acid (RCOOH) with emission of light in the visible region FMNH2 + O2 + RCHO RCOOH + FMN + H2O +h: All bacterial luciferases exhibit bioluminescent activity with aldehydes having the length of chain from 8 to 16 carbon atoms. Maximum luminescence intensity, the total quantum yield, light emission decay constant are determined by the luciferase type and length of chain of the aliphatic aldehyde [1]. The total quantum yield of the bioluminescent reaction is dened as the quantity of light quanta emitted in the course of a catalytic act. Actually, the quantum yield can be calculated as the ratio of the number of quanta released in the course of reaction to the number of molecules of each substrate processed in the course of reaction; or to the number of enzyme turnovers; or to the number of product molecules produced [2]. Oxidation of aldehyde to a respective fatty acid has been proved experimentally. Meanwhile, the evidence about the ratio of the fatty acid forming in the course of reaction and the light quanta emitted is fragmentary which is probably due to the diculties of evaluating experimentally microquantities of the fatty acid forming in the reaction. Only early works and for one substrate only which is not a natural substrate of the bacterial luciferase showed that the quantum yield of luminescence is not high [3, 4, 5]. Employment of radioactively labeled aldehyde made possible to demonstrate that for the luciferase of Photobacterium phosphoreum with decanal the quantum yield in terms of decanoic acid was 0.13 [3], for the luciferase of Photobacterium