Light detection of bacterial luciferase using hexanal and nonanal as substrates in pCMVlux-transfected COS7 cells

Abstract

　Numerous types of odorants are incorporated in foods, and they provide the specific flavor of different foods.　N-hexanal and n-nonanal are saturated aliphatic aldehydes with six and nine carbon chains, respectively, that are often included in foods.　 We hypothesize that odorants from food are taken into the body with other nutrients and exert specific physiological effects.　 Previously, we showed that hexanal or nonanal stimulated dopamine release in rat brain stratum slices and rat PC12 cells. 　Bacterial luciferases catalyze the oxidation of aliphatic aldehydes and FMNH2 into carboxylic acid and FMN, resulting in the emission of blue-green light.　A pCMVlux vector contains the gene cassette of human optimized synthetic luciferase under a cytomegalovirus promoter. 　In this study, I attempted to detect the light emitted by the bacterial luciferase in COS7 cells, which are derived from the kidney of African green monkeys, transfected with pCMVlux (COS7-pCMVlux).　The light intensity of the bacterial luciferase was detected after addition of nonanal and hexanal to COS7-pCMVlux cells.　The luciferase activity was higher with nonanal as the substrate than with hexanal.　Addition of reduced FMN to the assay solution enhanced the light intensity of the bacterial luciferase in the presence of nonanal.　On the other hand, after sonication of COS7-pCMVlux cells, the luciferase activity was low despite addition of reduced FMN and nonanal.　The half-life of the bacterial luciferase light emission with nonanal as the substrate was approximately 15 s in COS7-pCMVlux cells.　These results suggest that nonanal is taken into COS7 cells.