Unusual mechanism of hydrocarbon formation in the housefly: cytochrome P450 converts aldehyde to the sex pheromone component (Z)-9-tricosene and CO2.

Abstract

An unusual mechanism for hydrocarbon biosynthesis is proposed from work examining the formation of (Z)-9-tricosene (Z9-23:Hy), the major sex pheromone component of the female housefly, Musca domestica. Incubation of (Z)-15-[1-'4C1-and (Z)-15- [15,16-3H2jtetracosenoic These data demonstrate an unusual mechanism for hydrocarbon formation in insects in which the acyl-CoA is reduced to the corresponding aldehyde and then carbon-1 is removed as CO2. The requirement for NADPH and 02 and the inhibition by CO and the antibody to cytochrome P450 reductase strongly implicate the participation of a cytochrome P450 in this reaction.Long-chain hydrocarbons are abundant components in the cuticular lipids of plants and insects (1, 2), where they function to prevent water loss from the surface of the organism. In some insect species, including the housefly, Musca domestica, hydrocarbon components function as sex pheromones. The main component of the sex pheromone produced by the female housefly is (Z)-9-tricosene (Z9-23:Hy) (3), which functions as a short-range attractant and stimulant (4). In vertebrates, hydrocarbons function in the myelin sheath of peripheral nerves (5) and as components of uropygial gland secretions (6).The mechanism for hydrocarbon biosynthesis has proven to be elusive. Studies in the 1920s (7) suggested that two fatty acids condense head-to-head to form a ketone that is then reduced to the alkane. In an elegant series of experiments in the 1960s (reviewed in ref. -8), Kolattukudy and coworkers demonstrated that hydrocarbons are formed by the elongation of fatty acids, which are then converted to hydrocarbon by the loss of the carboxyl group, which was presumed to be a decarboxylation reaction (9,10). More recently, Kolattukudy and coworkers have obtained evidence from studies in a microorganism (11,12), a plant (13), a vertebrate (6), and an insect (14) that long-chain fatty acyl groups are reduced to aldehydes and then converted to hydrocarbons by a reductive decarbonylation mechanism. This mechanism does not require reduced pyridine nucleotides, and the carbonyl carbon is released as CO. In contrast, Gorgen and coworkers (15,16) presented evidence that 1-alkenes are formed by a decarboxylation mechanism in both plants and insects. We present evidence in this paper that hydrocarbon formation in the housefly occurs by the reduction of a long-chain acyl-CoA to an aldehyde that is then converted to the hydrocarbon and CO2 by a reaction that requires NADPH and 02 and involves cytochrome P450.

Biosynthetic pathway of aliphatic formates via a Baeyer–Villiger oxidation in mechanism present in astigmatid mites

“…However, exogenous aldehyde feeding experiments resulted in significant miticide activity, thus forcing consideration of alternative experiments. Aldehydes are known intermediates of hydrocarbons in insects (15)(16)(17)(18), and our own studies make it increasingly clear that aldehydes are also intermediates of hydrocarbons in acaridae. Because mites (Sancassania sp.…”

“…In mite lipid-derived 13 C-labeled OAME, odd-numbered carbon atoms 1, 3, 5, 7, 9, 11, 13, 15, and 17 were strongly labeled by 13 C. The 13 C-isotopic abundances of these nine carbon atoms were 689-919%. Conversely, 13 C-isotopic abundances of even-numbered carbon atoms-that is, 2 (standard signal), 4,6,8,10,12,14,16, and 18-were low at −15 to 37%, and these were judged to not be enriched by 13 C.…”

Dissecting ant recognition systems in the age of genomics

“…However, nearly all of these studies have been descriptive or correlational, and the biosynthetic pathways that underlie production and the mechanisms for generating molecular variation are not well understood. In fact, much of what we know about CHC synthesis in social insects relies on extrapolation from other, more well-studied, non-social insects, particularly species of Diptera [17][18][19][20].…”

“…Although the final biosynthetic step of CHC synthesis, the decarbonylation of long-chain fatty aldehydes to HCs, has long been believed to be catalysed by a P450 enzyme [18], the specific protein that performs this function has only recently been identified [20]. In Drosophila, oenocytedirected RNA interference (RNAi) was used to suppress gene expression of Cyp4g1 and (separately) NADPHcytochrome P450 reductase (CPR) [20].…”

Evidence for an Elongation/Reduction/C1-Elimination Pathway in the Biosynthesis of n-Heptane in Xylem of Jeffrey Pine

“…Long-chain waxy hydrocarbons in plants, animals, and microalgae apparently are synthesized by elongation of a C,, or C,, acyl COA to generate an acyl thioester one carbon longer than the hydrocarbon product (Cassagne and Darriet, 1977;Kolattukudy, 1980Kolattukudy, , 1987de Renobales et al, 1986;Templier et al, 1987;Vaz et al, 1988). The long-chain acyl COA is then reduced to an aldehyde and free COA, and the former undergoes either decarbonylation to form a hydrocarbon and carbon monoxide Kolattukudy, 1984, 1988;Kolattukudy, 1991, 1992;Yoder et al, 1992) or decarboxylation to form a hydrocarbon and carbon dioxide, as has been recently demonstrated for hydrocarbon biosynthesis in insects (Reed et al, 1994(Reed et al, , 1995Mpuru et al, 1996). n-Pentane found in developing peanuts also appears to arise from an acyl lipid, albeit directly from the lipoxygenase-catalyzed degradation of linoleic acid without the involvement of an aldehyde intermediate (Pattee et al, 1970(Pattee et al, , 1974Garssen et al, 1971;Johns et al, 1973).…”