Page 9 - Shimadzu Journal vol.3 Issue3

Drug Discovery

Phases of metabolism

Phase I Reactions Phase I Reactions
Oxidation Glucunoride
Reduction Glycine
Hydrolysis Glutathione, Acetylation etc

Phase I Phase II
CYP enzymes Active Transferases Conjugated
Drug
Metabolite Drug

NADPH NADP+ Glucuronide Sulphate
Glutathione Methyl

Studies in different animal species
The isoform composition and catalytic activity of cytochrome P450
enzymes varies for different animal species. Therefore, in vitro
metabolic studies are carried out with micosomes derived from
different animals and humans to identify interspecies variation. The
P450 isoform CYP3A4 is known to be mainly involved in metabolism
of xenobiotic. Microsomes and S9 are obtained by differential high
speed centrifugation from liver homogenate.

Cytosol

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