Question | Answer |
Xenobiotic metabolizing enzymes have been grouped into 2 phases. What does each one contain? | Phase I : Oxidation, reduction, and hydrolytic reactions .......... Phase II : conjugation reactions |
What are phase I reactions carried out by? | CYPs, Flavin-containing monoonxygenases (FMO) and Epoxide hydrolases (EH) |
What is considered the major "Metabolic clearing house" for both endogenous chemicals, and Xenobiotics. | The liver |
Drugs that are orally administered are absorbed in the gut and taken to the liver through the _____ vein, where they undergo significant metabolism | Portal |
Where would you find xenobiotics metabolizing enzymes within the cell? | intracellular membranes and cytosol |
What is Heme | The oxygen binding moiety found in hemoglobin |
What does the heme contains that allow it to bind oxygen in the CYP active site | Atom of iron in hydrocarbon cage |
What does CYPs use to carry out the oxidation of substrate? | O2 and H+ |
Metabolism of a substrate by a CYP consumes _____ molecule of molecular oxygen and produces an ______ and a ________ as a by product | One, oxidized substrate, molecule of water |
True/False: drug metabolizing CYPs and the CYPs that catalyze steroid and bile acids have very specific substrate preferences | FALSE, only CYPs that catalyze steroid and bile acids have that |
True/False: can can a single compound be metabolized by different CYPs at different rate? | True, They can even metabolize a single molecule at different positions on the molecule |
Generally, what is the half lives of drugs? What about endogenous compounds? | Drugs 3-30 hours .. Endogenous compounds - seconds or minutes |
What is one of the main reasons for the predominance of drug-drug interactions? | The feature of extensive overlapping of substrate specificities of CYPs |
What can inhibit the metabolism of some drugs leading to elevated plasma levels? | 2 drugs competing for binding to an active site .. one or both of these drugs would be inhibited |
What does a narrow therapeutic index for the drugs mean? | unwanted toxicities |
In naming CYPs what is the family, subfamily, and gene number . Example, CYP3A4 | 3- Family .. A-Subfamily .. 4- Gene number |
What are the CYPs involved in the metabolism of Xenobiotics? | There are 12 of them (CYP1A1, 1A2, 1B1, 2A6, 2B6, 2C8, 2C9, 2C19, 2D6, 2E1, 3A4, and 3A5) |
Where is the greatest amount of CYPs found? | The liver, and then lower amount in the lung, kidney, and CNS |
The expression of different CYPs can differ markedly as a result of: | - Dietary and environmental exposure to inducers
- Heritable polymorphic differences in gene structure
- Tissue specific expression patterns |
What are the most active CYPs for drug metabolism? | Those found in CYP2C, CYP2D, CYP3A sub-family |
Which CYP is most abundantly expressed in the liver and involved in the metabolism of over 50% clinically used drugs? | CYP3A4 |
What are some CYPs that exhibit polymorphism? | 2A6, 2C9, 2C19, 2D6 |
When does metabolism-related drug interactions occur? | when 2 drugs are co administered and subjected to metabolism by the same enzyme |