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Evidence for a sex pheromone metabolizing cytochrome P‐450 mono‐oxygenase in the housefly
Author(s) -
Ahmad Sami,
Kirkland Kenneth E.,
Blomquist Gary J.
Publication year - 1987
Publication title -
archives of insect biochemistry and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.576
H-Index - 66
eISSN - 1520-6327
pISSN - 0739-4462
DOI - 10.1002/arch.940060206
Subject(s) - cytochrome , microsome , biochemistry , housefly , monooxygenase , biology , cytochrome p450 , oxidase test , stereochemistry , metabolism , ketone , epoxide , chemistry , enzyme , organic chemistry , botany , larva , musca , catalysis
Direct evidence is presented for the role of a cytochrome P‐450 monooxygenase (called mixed‐function oxidase, or polysubstrate mono‐oxygenase, PSMO) in the metabolism of the sex pheromone (Z)‐9‐tricosene to its corresponding epoxide and ketone in the housefly. A secondary alcohol, most likely an intermediate in the conversion of the alkene to the ketone, was also tentatively identified. The results of in vivo and in vitro experiments showed that the PSMO inhibitors, piperonyl butoxide (PB) and carbon monoxide, markedly inhibited the formation of epoxide and ketone from (9,10‐ 3 H) (Z)‐9‐tricosene. An examination of the relative rates of (Z)‐9‐tricosene metabolism showed that males exhibited a higher rate of metabolism than females with the antennae of males showing the highest activity of any tissue/organ examined. The major product from all tissues/organs was the epoxide. Data from experiments with subcellular fractions showed that the microsomal fraction had the majority of enzyme activity, which was strongly inhibited by PB and CO and required NADPH and O 2 for activity. A carbon monoxide difference spectrum with reduced cytochrome showed maximal absorbance at 450 nm and allowed quantification of the cytochrome P‐450 in the microsomal fraction of 0.410‐nmol cytochrome P‐450 mg −1 protein. Interaction of (Z)‐9‐tricosene with the cytochrome P‐450 resulted in a type I spectrum, indicating that the pheromone binds to a hydrophobic site adjacent to the heme moiety of the oxidized cytochrome P‐450.