DD-transpeptidase

DD-transpeptidase is an enzyme that plays a crucial role in the final stages of cell wall synthesis in bacteria. It is also known as a penicillin-binding protein because it is the target of penicillin and other beta-lactam antibiotics.

Function

DD-transpeptidase catalyzes the cross-linking of the peptidoglycan layer in the bacterial cell wall, providing strength and rigidity to the cell structure. This is achieved by the formation of a peptide bond between the third amino acid of a pentapeptide and the terminal D-alanine of another pentapeptide.

Inhibition by antibiotics

Beta-lactam antibiotics, such as penicillin, inhibit the function of DD-transpeptidase. They mimic the D-alanine-D-alanine site of the peptide chain, binding to the active site of the enzyme and preventing it from cross-linking the peptidoglycan layer. This results in a weakened cell wall and eventual cell death.

Clinical significance

The inhibition of DD-transpeptidase by beta-lactam antibiotics forms the basis of their therapeutic use in the treatment of bacterial infections. However, resistance to these antibiotics can occur through the production of beta-lactamase enzymes that hydrolyze the beta-lactam ring, or through the alteration of the DD-transpeptidase enzyme itself.

See also

• Peptidoglycan
• Beta-lactam antibiotics
• Beta-lactamase
• Penicillin-binding protein