E bacteria can acquire resistance important wrt

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: is Penicillin can be seen to mimic acyl- D- Ala- D- Ala R C H N R H H S C Me O H N Me H H N O N Me O CH3 O CO2H Penicillin H CO2H Acyl- D- Ala- D- Ala R C But 6- methylpenicillin is inac#ve despite being a closer analogue H N Me H S O N O Me Me CO2H Mechanism of ac#on - bacterial cell wall synthesis Alternate hypothesis: Penicillin may act as an ‘umbrella’ inhibitor of transpep#dase D - A l a - D - A l a R C H N Blocked H S Me R O N O HO C Me CO2H H Ac#ve Site OH Acyla#on H N H S Me O O HN O Me CO2H OH Gram +ve and Gram - ve Cell Walls • Penicillins have to cross the bacterial cell wall in order to reach their target enzyme • Cell walls are porous and are not a barrier • The cell walls of Gram +ve bacteria are thicker than Gram - ve cell walls, but the former are more suscep#ble to penicillins Gram +ve and Gram - ve Cell Walls Gram +ve bacteria Thick porous cell wall Cell membrane Cell • Thick cell wall • No outer membrane • More suscep#ble to penicillins Gram +ve and Gram - ve Cell Walls Gram - ve bacteria Hydrophobic barrier Outer membrane Porin Lactamase enzymes L L L Periplasmic space Cell membrane Thin cell wall L Cell • Thin cell wall • Hydrophobic outer membrane • More resistant to penicillins Problems with Penicillin G • It is sensi#ve to stomach acids • It is sensi#ve to β- lactamases - enzymes which hydrolyse the β- lactam ring •  It has a limited range of ac#vity Problem 2 - Sensi#vity to β- Lactamases β- Lactamases • Enzymes that inac#vate penicillins by opening β- lactam rings...
View Full Document

This note was uploaded on 01/15/2014 for the course CHEM 167 taught by Professor Amaro during the Winter '13 term at UCSD.

Ask a homework question - tutors are online