Journal of Neuroscience, Vol 9, 1341-1353, Copyright © 1989 by Society for Neuroscience
A pheromone-degrading aldehyde oxidase in the antennae of the moth Manduca sexta
R Rybczynski, J Reagan and MR Lerner
Section of Molecular Neurobiology, Howard Hughes Medical Institute, Yale School of Medicine, New Haven, Connecticut 06510.
Antennae of the tobacco hornworm moths Manduca sexta contain an aldehyde
oxidase (AOX) that oxidizes aldehydes to carboxylic acids. The enzyme,
which is distinguishable from aldehyde-oxidizing activities in other
tissues, is secreted into the receptor lymph that bathes the primary
olfactory dendrites. First detectable about 3 d before eclosion, AOX levels
increase through the first day after eclosion. This parallels the
development of the antennal responsiveness to bombykal (a male attractant
aldehydic pheromone produced by female M. sexta) and trans-2-hexenal (an
aldehyde commonly found in leaves). The AOX is about 60% more abundant in
antennae of males than in antennae of females. The antennal AOX is a dimer
with Mr of 295 kDa and is capable of oxidizing a variety of aldehydes. Of
all aldehydes examined, the pheromone bombykal was the best substrate with
an apparent Km of 5 microM, whereas the next best substrate, benzaldehyde,
had an apparent Km of 255 microM. Using kinetic parameters estimated in
vitro and the assumption of first-order kinetics, the half-life of bombykal
in sensilla was estimated to be about 0.6 msec. The affinity of the
antennal AOX for bombykal, its location in the receptor lymph, and its
pattern of developmental expression all suggest that it plays a role in
modulating the sensitivity of adult M. sexta to aldehyde odors and, in
particular, the sensitivity of males to the pheromone bombykal.
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