Biosynthetic pathways, pheromones

Keywords Pheromone Biosynthetic pathways Hormonal regulation PBAN ... 

The chain shortening pathway has not been characterized in detail at the enzymatic level in insects. It presumably is similar to the characterized pathway as it occurs in vertebrates. These enzymes are a partial P-oxidation pathway located in peroxisomes [29]. The key enzymes involved are an acyl-CoA oxidase (a multifunctional protein containing enoyl-CoA hydratase and 3-hy-droxyacyl-CoA dehydrogenase activities) and a 3-oxoacyl-CoA thiolase [30]. These enzymes act in concert to chain shorten acyl-CoAs by removing an acetyl group. A considerable amount of evidence in a number of moths has accumulated to indicate that limited chain shortening occurs in a variety of pheromone biosynthetic pathways. 

PBAN binding to a receptor results in signal transduction events to stimulate the pheromone biosynthetic pathway (Fig. 5). Receptor activation results in the influx of extracellular calcium and has been demonstrated in a number of moths [163-168]. The increase in cytosolic calcium can directly stimulate pheromone biosynthesis in some moths [165-168] or it will stimulate the production of cAMP [169,170]. So far cAMP has only been implicated in signal... 

Fig. 5 Proposed signal transduction mechanisms that stimulate the pheromone biosynthetic pathway in Helicoverpa zea and Bombyx mori. It is proposed that PBAN binds to a G protein-coupled receptor present in the cell membrane that upon PBAN binding will induce a receptor-activated calcium channel to open causing an influx of extracellular calcium. This calcium binds to calmodulin and in the case of B. mori will directly stimulate a phosphatase that will dephosphorylate and activate a reductase in the biosynthetic pathway. In H. zea the calcium-calmodulin will activate adenylate cyclase to produce cAMP that will then act through kinases and/or phosphatases to stimulate acetyl-CoA carboxylase in the biosynthetic pathway...

FIGURE 3 Pheromone biosynthetic pathways commonly used in moth sex pheromone glands to produce precursors for specific blends of acetates, alcohols, or aldehydes. Cascades of precursors are produced by combinations of unique A- -desaturases and limited chain-shortening steps. The six precursors for the cabbage looper blend (Figure 2) are in boldface type. 

FIGURE 4 Proposed model for the interaction of PBAN with a receptor on the sex pheromone gland of a corn earworm female, and the resulting stimulation of acetyl-CoA carboxylase of the pheromone biosynthetic pathway. 

The chemical communication system used to attract mates involves not only the overt chemical signals but also indirectly a great deal of chemistry in the emitter and receiver. As an example, in emitting female moths, this includes enzymes (and cofactors, mRNA, genes) of the pheromone biosynthetic pathways, hormones (and genes) involved in... 

Fig. 8.1. Pheromone biosynthetic pathway in the cabbage looper, Trichoplusia ni. Key steps are chain shortening (—2C) and A11 desaturation (All). Circled acyl-coenzyme A (CoA) derivatives are reduced and acetylated to form the pheromone components. (Modified from Jurenka et al., 1994.)...

Sex pheromone component ratio in the cabbage looper moth altered by a mutation affecting the fatty acid chain-shortening reactions in the pheromone biosynthetic pathway. Insect Biochemistry and Molecular Biology 24 373-381. 

Jurenka R. A., Haynes K. F., Adlof R. O., Bengtsson M. and Roelofs W. L. (1994) Sex pheromone component ratio in the cabbage loopermoth altered by a mutation affecting the fatty acid chain-shortening reactions in the pheromone biosynthetic pathway. Insect Biochem. Mol. Biol. 24, 373-381. 

Martinez T., Fabrias G. and Camps F. (1990) Sex pheromone biosynthetic pathway in Spodoptera littoralis and its activation by a neurohormone. J. Biol. Chem. 265, 1381— 1387. 

The greenheaded leafroller moth, P. octo, utilizes a A10 desaturase in its pheromone biosynthetic pathway (Foster and Roelofs, 1988). A cDNA, designated Pocto-... 

Although E double bonds are uncommon in unsaturated fatty acids of animals, many have been found among the unsaturated components of lepidopteran pheromones. Early investigations of pheromone biosynthetic pathways showed that E isomers are not produced by isomerization of the Z double bonds, but rather are produced directly by the catalytic activity of desaturases possessing... 

Fabrias G., Barrot M. and Camps F. (1995) Control of the sex pheromone biosynthetic pathway in Thaumetopoea pityocampa by the pheromone biosynthesis activating neuropeptide. Insect Biochem. Mol. Biol. 25, 655-660. 

Fish R. H., Browne L. E., Wood D. L. and Hendry L. B. (1979) Pheromone biosynthetic pathways conversions of deuterium-labelled ipsdienol with sexual and enantioselectivity in Ips paraconfusus. Tetrahedron Lett. 17, 1465-1468. 

Fish R. H., Browne L. E. and Bergot B. J. (1984) Pheromone biosynthetic pathways conversion of ipsdienone to (-)-ipsdienol, a mechanism for enantioselective reduction in the male bark beetle, Ips paraconfusus. J. Chem. Ecol. 10, 1057-1064. 

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