Question

Explain how the selective induction of either Phase I (oxidative enzymes - e.g., cytochrome P-450) or Phase II (conjugative enzymes - e.g., glutathione transferase) enzymes can increase the toxicity of some chemicals while decreasing the toxicities of others

Answer 1

1. phase I enzymes -cytochrome P-450

this enzyme used in liver detoxification which functions as converting insoluble non-polar compound to the soluble polar compound so that it can be excreted from the blood. by this many xenobiotics are detoxified but there are some xenobiotics which are already non-toxic polar are converted into toxic form by cytochrome P-450.

an example is methanol which is non-toxic and the polar compound is converted into toxic compound called formic acid which causes methanol poisoning in humans.