BIOSYNTHESIS OF METHYL BRANCHED HYDROCARBONS OF THE GERMAN-COCKROACH BLATTELLA-GERMANICA (L) (ORTHOPTERA, BLATTELLIDAE)

The precursors and directionality of synthesis of the methyl branched cuticular hydrocarbons and the female contact sex pheromone, 3,11-dimethyl-2-nonacosanone, of the German cockroach, Blattella germanica, were investigated by radiotracer and carbon-13 NMR techniques. The amino acids [G-3H]valine, [4,5-3H]isoleucine and [3,4-14C2]methionine labeled the hydrocarbon fraction in a manner indicating that the carbon skeletons of all three amino acids serve as the methyl branch group donor. The incorporation of [1,4-14C2]- and [2,3-14C2]succinates into the hydrocarbon and acylglycerol/polar lipid fractions indicated that succinate also served as a precursor to methylmalonyl-CoA. Carbon-13 NMR analyses showed that [1-13C]propionate labeled the carbon adjacent to the tertiary carbon, and, for the 3,x-dimethylalkanes, that carbon-4 and not carbon-2 was enriched. [1-13C]Acetate labeled carbon-2 of these hydrocarbons. This indicates that the methyl branching groups of the 3,x-dimethylalkanes were inserted early in the chain elongation process. [3,4,5-13C3]Valine labeled the methyl, tertiary and carbon adjacent to the tertiary carbon of the methyl branched alkanes. Thus, the methyl branched hydrocarbon was formed by the insertion of methylmalonyl units derived from propionate, isoleucine, valine, methionine and succinate early in chain elongation. © 1990.