Regarding PBPs which is wrong? (LQ)
|A||Present on cell surface|
|B||Mutation gives rise to resistance|
|C||Target site of vancomycin|
|D||Target of imipenem|
Penicillin-binding proteins (PBPs) are a group of proteins that are characterized by their affinity for and binding of penicillin. They are a normal constituent of many bacteria; the name just reflects the way by which the protein was discovered. All beta-lactam antibiotics bind to PBP to have their effect of preventing cell wall construction by the bacterium
a. Penicillin binding proteins (PBPs) have enzymatic character and remove the terminal alanine in the process of forming a cross link with a nearby peptide.
b. Cross links between polysaccharides, polypeptides, peptidoglycan (murein, mucopeptide) give strength and rigidity to cell wall. Polysaccharides contain alternative aminosugars (N acetylglucosamine and N acetylmuramic acid). Terminal amino acid is d-alanine.
c. Importantly, PBPs are target site of beta lactam antibiotics. These range from low molecular to high molecular. PBPs mediate the final step in peptidoglycan synthesis. Importantly, this is a critical step in biosynthesis of cell wall of bacteriA. Therefore, beta lactam antibiotics kill bacterial by this mechanism.
d. Mutation in PBP leads to development of resistance (BG Katzung’ 10th Edition, 2010). Penicillins and cephalosporins kill the bacteria by destructing cell wall when bacteria are actively dividing.
e. Therefore, combining them with bacteriostatic agents is contraindicated.
(Remember: Beta lactamase is plasmid mediated, PBP is chromosomally mediated)