Chem167_L18_Jun4_final

Mechanism inhibited by penicillin blocked peptide

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Unformatted text preview: penicillin NAM L- Ala NAG D- Glu NAM L- Lys L- Ala D- Glu L- Lys NAG NAM NAM L- Ala NAG L- Ala NAG D- Glu L- Lys NAM D- Glu L- Ala NAM NAG L- Lys L- Ala D- Glu L- Lys NAM L- Ala D- Glu D- Glu L- Lys L- Lys Mechanism of ac#on - bacterial cell wall synthesis NAM NAG NAM L-Ala L-Ala D-Glu NAG SUGAR BACKBONE D-Glu L-Lys Gly Gly Gly Gly Gly L-Lys D-Ala D-Ala D-Ala Gly Gly Gly Gly Gly D-Ala PENICILLIN D-Alanine NAM NAG TRANSPEPTIDASE NAM L-Ala L-Ala D-Glu NAG D-Glu L-Lys D-Ala Gly Gly Gly Gly Gly Cross linking L-Lys D-Ala Gly Gly Gly Gly Gly SUGAR BACKBONE Mechanism of ac#on - bacterial cell wall synthesis • Penicillin inhibits final crosslinking stage of cell wall synthesis • It reacts with the transpep#dase enzyme to form an irreversible covalent bond • Inhibi#on of transpep#dase leads to a weakened cell wall • Cells swell due to water entering the cell, then burst (lysis) • Penicillin possibly acts as an analogue of the L- Ala- γ- D- Glu por#on of the pentapep#de chain. However, the carboxylate group that is essen#al to penicillin ac#vity is not present in this por#on Mechanism of ac#on - bacterial cell wall synthesis Alterna#ve theory- Pencillin mimics D- Ala- D- Ala. Normal Mechanism Peptide Chain Peptide Chain D-Ala OH Peptide Chain Peptide Chain D-Ala CO 2 H D-Ala Gly D-Ala O H OH Peptide Chain Gly Mechanism of ac#on - bacterial cell wall synthesis Alterna#ve theory- Pencillin mimics D- Ala- D- Ala. Mechanism inhibited by penicillin Blocked Peptide Chain Blocked H2 O O R C O H NH S N O H OH Me Me R O Gly C NH H O R S O NH H O HN CO2H C Me HN Me CO2H Blocked O S Me Me CO2H Irreversibly blocked Mechanism of ac#on - bacterial cell wall synthes...
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