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,
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.
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.