HLTH340 Study Guide - Glucuronosyltransferase, Phenacetin, Paracetamol
20 Dec 2013
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Discuss: recall that phase-2 metabolism enzymes (in ser or cytosol) attach conjugating group -- i. e. we are attaching something to the molecule. Notably, this works both with lipophilic xenobiotics (i. e. something that. Phase 1 didn"t touch) and their phase-1 metabolites (something that. Phase 1 did touch: the only requirement is for available oxygenated functional groups (often from. Discuss: phase-2 reactions convert lipophilic compounds to hydrophilic metabolites. This is because (as suggested above), it attaches conjugating group -- which notably is anionic (negative charge: as a result, there is ready excretion of hydrophilic conjugates by glomerular ultrafiltration in kidney. Recall that it is passive -- no energy required. However, this means that it is first-order excretion kinetics (slow) Because if they were not conjugated and still lipophilic, they could just come back: however, notably, bacterial enzymes in large intestine may remove conjugating groups by hydrolysis. Phase-1 and phase-2 metabolism often work in tandem process to enable elimination of drugs and xenobiotics.
