Methyl-branched fatty acids present in the integument of the German cockroach, Blattella
germanica, were identified by gas chromatography-mass spectrometry of their methyl
esters and reduction products (alkanes) as n-3-, n-4-, n-5-, n-7-, n-8-, and n-9-monomethyl
fatty acids and as n-5,9-, n-3,9-, and n-3,11-dimethyl fatty acids with 16 to 20 total
carbons. These fatty acids have the same branching patterns as do the major hydrocarbons
of this insect, including 3,11-dimethylnonacosane, the precursor to the major contact
sex pheromone, and are presumed to be intermediates in hydrocarbon formation. A novel
microsomal fatty acid synthetase (FAS) located in the integument of this insect incorporated
[methyl-14C]methylmalonyl-CoA into methyl-branched fatty acids as demonstrated by
radio-high-performance liquid chromatography. A cytosolic FAS is also present in the
integument. Both the microsomal and the soluble FAS incorporated [methyl-14C]methylmalonyl-CoA
into fatty acids, but only the microsomal FAS was able to efficiently use methylmalonyl-CoA
as the sole elongating agent. This is the first report of the characterization of
methyl-branched fatty acids from the integument of an insect and of an integumental
microsomal FAS that incorporates methylmalonyl-CoA into branched fatty acids.