CRUCIAL difference between Blactams VS Vancomycin - USMLE Forums
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Old 05-12-2014
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Help CRUCIAL difference between Blactams VS Vancomycin

Hi guys, i see that this crucial difference is very high yield.
i get kinda confused and want to have it straight out.
please correct me if im wrong,

B LACTAMS: they BLOCK transpeptidases (PBP) which make the peptidoglycan PRECURSORS for adding into the peptidoglycan wall, so no precursors, no crosslinking to the cell wall, no cell wall: destruction

VANCOMYCIN: they BIND covalent to the D-ala D-ala portion on the CELL WALL PRECURSORS (cell wall glycoproteins), so when they get incorporated into cell wall by transpeptidades (PBP) onto the newly made peptidoglycan wall, the ENTRANT peptidoglycan will not bind, cell wall falls apart: destruction

please correct with this, or confirm!!! help me out, thanks!!!
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Last edited by drpisho; 05-12-2014 at 07:38 AM.
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Old 05-12-2014
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Quote:
Originally Posted by drpisho View Post
Hi guys, i see that this crucial difference is very high yield.
i get kinda confused and want to have it straight out.
please correct me if im wrong,

B LACTAMS: they BLOCK transpeptidases (PBP) which make the peptidoglycan PRECURSORS for adding into the peptidoglycan wall, so no precursors, no crosslinking to the cell wall, no cell wall: destruction

VANCOMYCIN: they BIND covalent to the D-ala D-ala portion on the CELL WALL PRECURSORS (cell wall glycoproteins), so when they get incorporated into cell wall by transpeptidades (PBP) onto the newly made peptidoglycan wall, the ENTRANT peptidoglycan will not bind, cell wall falls apart: destruction

please correct with this, or confirm!!! help me out, thanks!!!


The B lactams block the cross linkage of transpeptidase and so peptidoglycan is not well linked and as such cell wall not formed well.

Vancomycin actually disrupt the formation of the peptidoglycan so here we don't have peptidoglycan formed.
I hope u get it.
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Old 05-12-2014
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For the B lactams; The final transpeptidation step in the synthesis of the peptidoglycan is facilitated by DD-transpeptidases which are penicillin-binding proteins (PBPs).
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Old 05-12-2014
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Originally Posted by nsesereso View Post
For the B lactams; The final transpeptidation step in the synthesis of the peptidoglycan is facilitated by DD-transpeptidases which are penicillin-binding proteins (PBPs).
hey thanks!! so vanco binds to cellwall precursors so no peptidoglycan precursors and obvious no synthesis of peptidoglycan wall, and NOTHING to do in the transpeptidation? (is this what you mean)
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Old 05-12-2014
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hey thanks!! so vanco binds to cellwall precursors so no peptidoglycan precursors and obvious no synthesis of peptidoglycan wall, and NOTHING to do in the transpeptidation? (is this what you mean)

Exactly!
The binding of vancomycin to the D-Ala-D-Ala prevents cell wall synthesis in two ways. It prevents the synthesis of the long polymers of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) that form the backbone strands of the bacterial cell wall, and it prevents the backbone polymers that do manage to form from cross-linking with each other. So the peptidoglycan cell wall is not formed.
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