IP Endocrinology

Microsomal reactions involved in the formation of hydrocarbons and the contact sex pheromone in Blatella germanica integument

M.P. Juárez 1 & G. J. Blomquist 2

1 Inst. Investig. Bioquím. La Plata, Fac. Cs. Méd, UNLP, calles 60 y 120, La Plata 1900, Argentina. 2 Dept. Biochem., Univ. Nevada, Reno, NV 89557, USA

The major cuticular hydrocarbon component of the german cockroach Blatella germanica, 3,11-dimethylnonacosane, and the major female contact sex pheromone, 3,11-dimethyl-2-nonacosanone, are metabolically linked through hydroxylation and oxidation steps. We report that the integument is the site of pheromone synthesis. Integumental fatty acid synthetases (FASs) were shown to produce the methylbranched fatty acid precursors. Elongation of fatty acyl-CoAs to very long chain fatty acids, and the final step in the synthesis of the major component of the sex pheromone, the conversion of 3,11-dimethyl [11,12 3 H]nonacosane to 3,11-dimethyl [11,12 3 H]-2-nonacosanone, were studied in integumental microsomes. Incubation of [1-14 C]palmitoyl-CoA, malonyl-CoA and NADPH resulted largely in the production of [ 14 C]C18-CoA with minor amounts of C20, C22, C24, C30 and C32 acyl moieties. Similar experiments with [1-14 C]stearoyl-CoA rendered C20-CoA as the major product, minor peaks of C22 and C24-CoAs were also detected. After solubilization of the microsomal FAS, kinetic parameters were determined radiochemically or measuring NADPH consumption by spectrophotometry. The reaction velocity was linear up to 10 min incubation time, and with protein concentration up to 0.025 ?g/?l. The effect of the chain length on the reaction velocity was compared for palmitoyl-CoA, stearoyl-CoA and eicosanoyl-CoA, the optimal sustrate concentration was 12 ?M for C16-CoA, 9 ?M for for C18-CoA, and 4 ?M for C20-CoA. Studies were performed to examine in vitro the last steps in the synthesis of the contact sex pheromone after incubation of microsomal preparations with [11, 12-3 H]3,11-dimethylnonacosane or [11,12-3 H ]3,11-dimethyl-2-nonacosanol. After 30 min at pH 7.8, in O2 atmosphere, the alkane was converted into methylketone and the corresponding alcohol. When the sustrate was the C29-ol, almost 90% was metabolized into the sex pheromone.

Index terms: elongases, acyl-CoA, hydrocarbons, german cockroach

Copyright: The copyrights of this original work belong to the authors (see right-most box in title table). This abstract appeared in Session 4 – CHEMICAL AND PHYSIOLOGICAL ECOLOGY Symposium and Poster Session, ABSTRACT BOOK I – XXI-International Congress of Entomology, Brazil, August 20-26, 2000.