Phase I metabolism
• Functionalization reactions
• Create or reveal a “handle” for Phase II metabolism
– Oxidation : (RH ROH)
– Reduction : (C=O CH-OH)
– Hydrolysis : (R-CO2
-CH3 RCOOH + CH3OH)
• Makes the molecules more susceptible for Phase II reactions
• Oxidation the most important
- Catalyzed by a super-family of enzymes: the Cytochrome P450s
• Phase I reaction produces reactive molecules, which may
be more toxic than the parent molecule