Metabolic Phases: Phase II Flashcards
Phase II reactions includes the process of
conjugation.
What is Phase II metabolism?
It is the process by which foreign or endogenous groups are added to the xenobiotic that are polar and readily available in the body.
Reactions in Phase II
- Glucuronidation
Glucuronidation (Glucuronic Acid Conjugation) is
A major pathway used by all mammals for xenobiotic species except for the cat family.
Conjugation with glucuronic acid involves
nucleophilic attack by the electron-rich oxygen, sulfur or nitrogen atom in the xenobiotic at the C-1 carbon atom of the glucuronic acid moiety.
Conjugation with hydroxyl groups gives
ether glucuronides.
Conjugation with carboxylic acids gives
ester glucuronides.
Sulfonation (Sulphate Conjugation) is
The addition of a sulphite group (SO3) is a major pathway used by mammals for xenobiotics, especially those that undergo O glucuronidation. The cofactor that aids this is 3’phosphoadenosine- 5’-phosphosulfate (PAPS).
What is catalysed the sulfonation reaction?
sulfotransferase (SULT)?
What is Acetylation?
A major pathway used by mammals for xenobiotics. It is the addition of an acetyl group (-COCH3), especially those that are aromatic amines (R-NH2) which are converted to aromatic amides (R-NH- COH3) and hydrazine (R-NH-NH2) that are converted to hydrazides (R-NH-NH-COH3).
What does Acetylation use ?
It uses Acetyl CoA as it coezyme
What cataylises acetylation reaction?
N-Acetyltransferase (NAT) are the enzymes that catalyse the reaction
What are the two types of N-
- NAT1 & 2. NAT2
Acetylation does not make the xenobiotic more _____, but it makes it less _____ and how is this achieved?
Acetylation does not make the xenobiotic more hydrophilic, but it makes it less toxic. This reduction is done by CYP 450
Where is NAT 1 & NAT2 found?
- NAT1 – Found in most tissues and red blood cells
- NAT2 – Found mostly in the Kupffer cells of the liver
