Another stress factor to deal with is endogenous aromatic compounds as well as environmentally-derived
xenobiotic compounds (organic pollutants, toxins, drugs), which are all
being metabolized in the biotransformation pathway [82]. The most important enzyme families
participating in this pathway are cytochrome p450s/monooxygenases, glutathione S-transferases
and ATP-binding cassette (ABC) transporters. Monooxygenase activity was enriched
among PSGs in the Hexapoda lineage and represented by monooxygenase and two cytochromes
P450 (S5 Table). This protein family is well-known for its functional diversification in
hexapods and associated with differences in life history and ecology of insect species [83].
From a functional perspective, monooxygenase activity is part of the first step in biotransformation
(phase I), during which organic compounds are oxidized so that they become watersoluble.