Phase II Drug Metabolism and Conjugation

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What is the primary role of Phase II enzymes in detoxification?

To transform toxic reactive molecules into less reactive species (correct)

To catalyze the oxidation of xenobiotics

To synthesize UDP-glucuronic acid

To inhibit the activity of Phase I enzymes

What is the function of UDP-glucuronic acid in the glucuronidation reaction?

It acts as a cofactor for the UGT enzyme

It is the product of the glucuronidation reaction

It is the substrate that is transferred to the xenobiotic handle (correct)

It provides the energy required for the conjugation reaction

Which of the following is NOT a type of 'handle' that can be conjugated by Phase II enzymes?

Ester groups (correct)

Hydroxyl groups

Thiol groups

Carboxylic acid groups

What is the significance of the localization of UGTs in the ER membrane?

It allows for the rapid metabolism of xenobiotics from Phase I to Phase II Signup and view all the answers

What is the consequence of UGT-catalyzed reactive metabolites for drugs containing carboxylic acids?

They can covalently modify proteins Signup and view all the answers

What is the characteristic of the gene expression of UGT1A and UGT2B subfamilies?

They are differentially spliced to produce different isoforms Signup and view all the answers

What is the consequence of UGT substrate IBufenac rearranging to the reactive species faster than its methyl-substituted analog ibuprofen?

Hepatotoxicity is exhibited in humans Signup and view all the answers

What is the role of sulfotransferases in Phase II enzyme conjugation?

They conjugate amino, hydroxy, and carboxyl groups with an activated sulfo donor Signup and view all the answers

What is the result of the high acidity of the sulfate group in sulfation reactions?

The products are completely charged at physiological pH Signup and view all the answers

What is a characteristic of phenols in sulfation reactions?

They are particularly good substrates for sulfation Signup and view all the answers

Why do glucuronidation reactions predominate over sulfation reactions at high doses?

Because the supply of sulfate in the cell is limited Signup and view all the answers

Where are human SULTs organized in the cell?

In the golgi (the outside) Signup and view all the answers

Phase II Drug Metabolism and Conjugation

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