Metabolism of xenobiotics is done by -

Ans. is 'b' i.e., Cytochrome p450 o Biotransformation reactions (metabolism) of drugs can be classified :A. Non-synthetic (phase I) reactions# Metabolism brings about a change in the drug molecule by:1. Oxidation2. Reduction3. Hydrolysis4. Cyclization5. Decyclization# The new metabolite may retain biological activity or it may be an inactive metabolite.# Oxidation is the most important metabolizing reaction.# The most important enzyme for oxidation reaction is cytochrome P450B.Synthetic (phase II or conjugation) reaction# Metabolism involves union of the drug with one of several polar (water-soluble) endogenous molecules that are products of intermediary metabolism, to form a water-soluble conjugate which is readily eliminated by kidney or, if the molecular weight exceeds 300, in the bile.# Phase II metabolism almost invariably terminates biological activity, i.e. metabolites are usually inactive.# Reactions are:-1. Acetylation2. Glucuronide conjugation3. Glycine conjugation4. Glutathione conjugation5. Sulfate conjugation6. Methylation7. Neucleotide synthesis