Pheromones labelling studies

Specific chain length fatty acids could be produced in two ways. One is through the action of a thioester hydrolase that interacts with fatty acid synthetase to produce fatty acids shorter in length. Aphids produce myristic acid (14 carbons) and a specific thioester hydrolase releases the fatty acid from fatty acid synthetase after 6 additions of malonyl-CoA. If the hydrolase is not present then the fatty acid synthetase produces stearic acid [27]. A specific thioester hydrolase was ruled out in the biosynthesis of moth sex pheromones because labeling studies showed that longer chain length fatty acids were incorporated into shorter chain length pheromone components [22,28]. 

Figure 3.2 A. Possible biosynthetic pathways for producing the sex pheromone components Z9-14 OAc and Z9,E12-14 OAc in the almond moth. The Z9-14 CoA and Z9,E12-14 CoA derivatives are reduced and acetylated to make the acetate esters. B. The biosynthetic pathway as determined by deuterium labeling studies presented in Figure 3.3.

What do SNMPs do The identification of Apo/SNMPl followed photoaffinity labeling studies that tentatively identified a 69 kDa protein as a pheromone receptor (Vogt et al., 1987) however, a role as pheromone receptor seems highly unlikely because SNMPs appear to associate with most olfactory neurons, and are neither 7-transmembrane domain receptors nor show the diversity expected for ORs. SNMPs certainly show no similarity to the presumed ORs identified in D. melangaster, A. gambiaea and H. virescens (Clyne et al., 1999 Vosshall et al., 1999 Hill et al., 2002 Krieger et al., 2002). If SNMPs are not ORs, what are they ... 

The site of pheromone production is varied amongst the insects just as there are variable structures in the different orders. Several reviews are available detailing the ultrastructure of these glands [9-11]. Evidence that pheromone biosynthesis occurs in these cells and tissues requires that the isolated tissue be shown to incorporate labeled precursors into pheromone components. In the more studied model insects this criteria has been met. 

Bjostad L. B. and Roelofs W. L. (1986) Sex pheromone biosynthesis in the red banded leafroller moth studied by mass-labeling with stable isotopes and analysis with mass spectrometry. J. Chem. Ecol. 12, 431-450. 

The assembly of the carbon skeletons of these unusual hydrocarbons was first studied in Carpophilus freemani Dobson, through careful GC-MS and Nuclear Magnetic Resonance (NMR) studies of the incorporation of 2H or 13C-labeled precursors (Petroski et al., 1994). Assembly of the carbon skeleton of the aggregation pheromone of C. freemani, (2 , 4 , 6ii)-5-ethyl-3-methyl-2,4,6-nonatriene, involves initiation with acetate elongation with first propionate (to provide the methyl branch), then butyrate (to provide the ethyl branch) and chain termination with a second butyrate (Figure 6.7). At some point, loss of C02 from one of the butyrate units occurs to yield the appropriate hydrocarbon, but Petroski et al. (1994) were unable to determine which of the butyrate units loses its carboxyl group. Bartelt and Weisleder (1996) studied the biosynthesis of 15 additional methyl- and/or ethyl-branched, tri- and tetraenes in the related... 

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