MGY377H1 Final: Study notes for exam
27 Dec 2011
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has n-acyl group, beta-lactam ring, thiazolidine ring. resistance arises by acquiring a plasmid that carries the penicillinases (beta- lactamases) penicillins not hydrolyzed by penicillinases ex. penicillins can be modified to be active against gram-negatives and with negatively charged substitutes. beta-lactam ring has an amide bond that mimics the d-ala-c-ala bond in a wall peptide. Inhibition of transpeptidases by penicillin involves a stable enzyme-penicillin complex. penicillins irreversibly inhibit transpeptidases by acting as a substrate for the transpeptidase enzyme. transpeptidases attack the bond in penicillin that mimics the d-ala-d-ala bond in wall peptides in a manner that is similar to the first step of transpeptidation. however, the bulky side groups interfere with the subsequent step where the acyl-enzyme intermediate is resolved. enzyme gets stuck with a penicillin molecule attached to its catalytic serine residue. frequently given to patients allergic to penicillins. active against many penicillinase-producing staphylococci and gram-negative bacteria.
