The earliest studies of oxidative metabolism of insecticides in insects in the 1950's closely followed and paralleled similar studies on drug and insecticide metabolism in vertebrates. In vivo and intact tissue experiments were then followed by experiments with cell-free extracts and “microsomes”. As details of the enzymatic requirements of such reactions in microsomal fractions emerged, it rapidly became clear that the enzyme system - initially called “mixed function oxidase” and only later P450 - was essentially the same in vertebrates and insects. Both M. Agosin and L. Terriere (personal communications) related the skepticism of the (vertebrate) toxicology community in the early 1960's. Insects couldn't possibly metabolize chemicals the same way as rat liver ?

1958

Fenwick (1958) reported the bioactivation of schradan (OMPA) by homogenates and a post-mitochondrial fraction from locust (Schistocerca gregaria) fat body. The reaction, which produced an esterase inhibitor (p-nitrophenylacetate to p-nitrophenol activity), was dependent on NADPH and aerobic conditions. This cell free system also bioactivated dimefox. Both insecticides are phosphoroamidates, and bioactivation to the esterase inhibitors is thought to proceed by N-hydroxylation. Fenwick noted that the “strange need for a reducing agent in an oxidative process” has already been observed in mammalian drug metabolism (Brodie, 1956; Velick, 1956), and that the reaction mechanism might be of the type discussed by Mason.

1960s

Although synergists of pyrethrum had been known and used for some time, Sun and Johnson (1960) first suggested that they acted by inhibiting the oxidative metabolism of insecticides. Casida (1970) published a detailed review on the chemical diversity of synergists.

1961:

Agosin et al. (1961) described a microsomal preparation from whole adult male Blattella germanica that was able to convert DDT to a metabolite tentatively identified as “Kelthane” (dicofol), i.e. C1-hydroxy DDT. Highest activity was observed in the presence of NADP+, an NADPH-regenerating system, Mg++ and nicotinamide. Nearly half of the crude homogenate activity was found in the microsomal fraction, with some activity in the “nuclei” and “mitochondria” fractions. Activity was also reported for house fly and American cockroach preparations. This report followed earlier work in vivo that had shown conversion of DDT to kelthane in house flies (Hoskins et al, 1958, Hoskins and Witt, 1958) and Drosophila (Tsukamoto 1959,1960).

1962:

Arias and Terriere (1962) prepared microsomes by differential centrifugation of whole house fly homogenates (larvae, pupae or adults). These microsomes converted naphthalene by hydroxylation to 1-naphthol and 1,2-dihydro-1,2 dihydroxynaphthalene. NADPH-dependence was only observed with microsomes from older adults.

1965

Ray is usually credited with the first report of insect P450 spectra in the house fly, Blattella germanica and Periplaneta americana (J.W.Ray, Pest Infestation Research, p 59, HMSO, 1965; cited in Ray, 1967), but the first publication is that of 1967. Microsomes from whole adult house flies showed a substantial P450 peak that was converted to P420 upon addition of deoxycholate (Ray, 1967). Garfinkel (1963) had earlier reported “traces” of P450 in microsomes from lobster (Homarus americanus) gills (but none in hepatopancreas, green gland, gonads; one may surmise that the other tissues were consumed).

1970s:

Evidence of P450 induction by insecticides and other chemicals (phenobarbital)

Evidence of P450 multiplicity in insects, mostly from partial purification studies

Description of developmental changes in P450 levels and P450-dependent activities in insects.

1972:

Description of microsomal P450 activities in the freshwater crayfish, Cambarus sp. (Decapoda, Pleocyemata)(Khan et al., 1972)

1977:

Fluctuations in a P450 activity (benzo(a)pyrene hydroxylation) in homogenates of blue crab (Callinectes sapidus, Decapoda, Brachyura) green glands during a molt cycle (Singer and Lee, 1977)

1985:

Agosin (1985) and Hodgson (1985) have extensively reviewed the early literature of research on insect microsomes, microsomal oxidations of (mostly) insecticides and the emerging field of P450. These two reviews, along with that of Brooks (1979) are essential sources on the early in vivo and in vitro work.

1989:

Cloning of the first insect P450, house fly CYP6A1 (Feyereisen et al., 1989). A cDNA expression library was screened with antibodies to a partially purified P450 fraction from adult house fly abdominal microsomes.

1994:

Functional expression of house fly CYP6A1 and P450 reductase in E. coli (Andersen et al. 1994)

1996:

Cloning and functional expression of house fly cytochrome b5 (Guzov et al., 1996)

1998:

Cloning and functional expression of a mitochondrial P450, house fly CYP12A1 (Guzov et al., 1998).

2000-2001:

Sequencing of the first insect genome, Drosophila melanogaster (Adams et al., 2000), and annotation of its CYPome (Tijet et al., 2001)

2009-2011

Sequencing of the first crustacean genome, Daphnia pulex (Colbourne et al., 2011), and annotation of its CYPome (Baldwin et al., 2009).

2011:

Sequencing of the first chelicerate genome, Tetranychus urticae and annotation of its CYPome (Grbic et al., 2011).