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#transpeptidase

2 public questions tagged with this topic.

Microbial Physiology

Which enzyme is involved in the cross-linking of peptidoglycan?

After glycan polymerization by transglycosylases elongating alternating N-acetylglucosamine and N-acetylmuramic acid strands, final strength requires crosslinking of stem peptides attached to MurNAc. Stem typically comprises L-alanine, D-glutamate, meso-diaminopimelic acid or L-lysine, and terminal D-alanyl-D-alanine dipeptide. DD-transpeptidases, members of penicillin-binding protein family including PBP1a, PBP1b, PBP2a, and PBP3, perform nucleophilic attack where serine in active site forms bond with penultimate D-alanine, releasing terminal D-alanine, then transfers acyl-intermediate to ami

Ref: Vollmer et al., FEMS Microbiol Rev 2008, Peptidoglycan Crosslinking; Lovering et al., Ann Rev Biochem 2012, PBPs.

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Microbial Physiology

Which enzyme is inhibited by penicillin?

Bacterial peptidoglycan final crosslinking step catalyzed by transpeptidases penicillin binding proteins class B enzymes PBP2 for elongation, PBP3 FtsI for division. They cleave C terminal D alanine D alanine dipeptide from pentapeptide side chain MurNAc L Ala D Glu mDAP D Ala D Ala, forming acyl enzyme intermediate through active site serine nucleophile, then transfer to amino group acceptor meso diamino pimelic acid or L lysine of neighboring strand creating peptide crossbridge essential for wall rigidity. Beta lactam antibiotics penicillin contain four membered ring mimicking D Ala D Ala co

Ref: Tipper & Strominger, PNAS 1965, Penicillin inhibits transpeptidase PBP crosslinking peptidoglycan.

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