Woah, why are these enzymes in the brain at all. Especially metabolic CYP enzymes, which primarily metabolise xenobiotic compounds into more polar metabolites. I don't see any biological usefulness for them being in the brain. Enzymes don't metabolise compounds "because they are toxic". They metabolise them because they are exogenous and thus have a chance of being toxic, and they don't necessarily convert them into a non toxic metabolite; they convert them into a more polar metabolite.
If CYPs were in the brain they'd be making drugs more polar metabolites within the brain and thus delaying excretion; the polar molecules would be trapped in the brain because they can't cross the BBB. If anything this is going to lead to increased toxicity of many compounds. If someone with more biological knowledge than me could suggest why these enzymes exist at all in the brain that would be appreciated.