The human body, in order to protect itself against the potential
harmful insults from the environment, is equipped with
drug or xenobiotic metabolising enzymes (DMEs or XMEs)
that play a central role in the biotransformation, metabolism
and/or detoxification of xenobiotics or foreign compounds, including
different kinds of pollutants. XMEs include a variety
of enzymes such as cytochrome P450 (P450 or CYP), epoxide
hydrolase, glutathione transferase, UDP-glucuronosyltransferase,
sulfotransferase, NAD(P)H quinone oxidoreductase 1, and
aldo-keto reductase.