D -alanine transpeptidase
| D -Ala- D -Ala-carboxypeptidase ( Escherichia coli K12) | ||
|---|---|---|
| Mass / length primary structure | 844 amino acids | |
| Secondary to quaternary structure | Monomer, homodimer, heterotrimer | |
| Isoforms | several | |
| Identifier | ||
| Gene name (s) | mrcB (EcoGene) | |
| External IDs | ||
| Enzyme classification | ||
| EC, category | 3.4.16.4 , serine proteases | |
| Response type | Separation of peptide bonds | |
| Substrate | (Ac) 2 - L- Lys- D -Ala- D -Ala | |
| Products | (Ac) 2 - L -Lys- D -Ala + D -Ala | |
| Occurrence | ||
| Parent taxon | bacteria | |
D -alanine transpeptidase (more precisely: D -alanyl- D -alanine carboxypeptidase , also DD-transpeptidase ) is an enzyme thatoccursexclusively in bacteria . It is responsible for the cross-linking of the carbohydrate building blocks ( peptidoglycans ) of the bacterial cell walls and thus for their stability. The enzyme is the starting point for beta-lactam antibiotics (for example penicillin ), which irreversibly inhibit its enzymatic activity; The antibiotic forms a firm bond with amino acids of the active center and thus prevents a new synthesis of the cell wall, which leads to lysis (bactericidal effect) or cell division is stopped, which in turn has a bacteriostatic effect.
DD transpeptidase is a penicillin-binding protein . There are several families of enzymes with comparable activity, which on the one hand belong to the serine proteases and on the other hand to the metalloproteases . There are four families of enzymes which have different origins: D -alanyl- D -alanine-carboxypeptidase A, B and C, and zinc D -Ala- D -Ala-carboxypeptidases.
Catalyzed reaction
The cross-linking of the cell wall takes place between peptide residues that are connected to the carbohydrate content of the peptidoglycans via N-acetylmuramic acid . These are in particular D -alanine residues. It primarily plays a role in cell division, since parts of the cell wall have to be re-synthesized here.
literature
- Joachim Rassow : Biochemistry . Ed .: Michael Gekle et al. Georg Thieme Verlag, Stuttgart 2008, ISBN 978-3-13-125352-1 , p. 43 f .
Individual evidence
- ↑ UniProt P02919
- ↑ IPR018044 Peptidase S11, D-alanyl-D-alanine carboxypeptidase A. In: InterPro 32.0. EBI, accessed May 9, 2011 .
- ↑ Peptidase family S12 (D-Ala-D-Ala carboxypeptidase B family). In: MEROPS 2011. Sanger, accessed on May 9, 2011 (English).
- ↑ IPR000667 Peptidase S13, D-Ala-D-Ala carboxypeptidase C. In: InterPro 32.0. EBI, accessed May 9, 2011 .
- ↑ Peptidase family M15. In: MEROPS 2011. Sanger, accessed on May 9, 2011 (English).