Question

Describe the importance of Phase I and Phase Il enzymes in toxicokinetics.

Answer 1

Phase 1- also called as non-synthetic and non- conjugated phase include reaction which catalyse oxidation , reduction and hydrolysis of toxins.

in this reaction , small polar functional group like -OH, -NH2 , -COOH etc are either added or unmasked on the lipid soluble toxin so that resulting product may either undergoes phase 2 reaction or either are directly excreted.

this phase helps in removing of toxins either directly by excretion or by inhancing phase 2 reaction.

three types of reaction occur-

1. oxidation

2. reduction

3. hydrolysis

Phase 2- conjugation of a functional group to the toxin or its metabolite to make it water soluble. this reaction involve combination of toxin or it phase 1 metabolites with an endogenous substances to form a high polar product , which can efficiently excreted from the body.

this reaction include -

conjugation with glucuronic acid

conjugation with sulphate

conjugation with acetyl group

conjugation with methyl group

glycine connjugation