The Influence of Aldehyde Chain Length upon the Relative Quantum Yield of the Bioluminescent Reaction of Achromobacter Fischeri.

A long chain saturated fatty aldehyde is required for maximal light emission in the bioluminescent reaction catalyzed by the enzyme, bacterial luciferase, purified from extracts of Achromobatter &ch.t&. Since the discovery of this requirement by Strehler and Cormier (1, 2), very little has been learned about either the chemical role of aldehyde in the reaction or the nature of the presumed naturally occurring aldehyde-like compound. Indeed, it is not yet definitely known whether aldehyde is actually consumed in the reaction, as suggested by the experiments of McElroy and Green (3) and of Cormier and Totter (4), or whether it has instead a catalytic-like role, as suggested by Strehler (5). With respect to the specificity of the reaction, Strehler and Cormier (2) showed that several different aldehydes stimulate light emission, albeit with varying degrees of effectiveness as judged by the initial maximal intensity (initial rate) of the reaction. Additional studies with dark mutants of the luminous bacteria, as well as the reaction in vitro with partially purified enzyme, were reported by Rogers and McElroy (6). In view of the increased knowledge about the mechanism of the bioluminescent reaction in bacteria (7, 8), information concerning the effects of different aldehydes is of considerable interest. In the present study, homologous saturated straight chain aliphatic aldehydes ranging from 3 to 20 carbon atoms were examined with regard to their effect upon the reaction. The chemiluminescent quantum yield of the reaction has been found to be different with aldehydes of different chain length. This effect is believed to be localized at a step involved in either the creation or dissipation of the excited state. The reaction requires, in addition to the aldehyde and enzyme, reduced flavin mononucleotide and oxygen. It has been recently shown that the light-emitting reaction involves first the reduction of enzyme by reduced flavin mononucleotide, followed by the combination of reduced enzyme with oxygen (Fig. 1). Added aldehyde is not required for these reactions, and the enzyme intermediate resulting from these two steps has an appreciable lifetime which may vary (depending upon experi-