The presence of D-amino acids in the cross links of peptidoglycan laye...
D-amino acids are most likely present in cross links of peptidioglycan layer as proteases easily cleave L-amino acids.
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The presence of D-amino acids in the cross links of peptidoglycan laye...
D-amino acids are mirror images of L-amino acids, differing only in the orientation of their functional groups. In the context of the peptidoglycan layer, which is a major component of bacterial cell walls, the presence of D-amino acids in the cross-links is most likely because most peptidases can only cleave L-amino acids.
Explanation:
Peptidoglycan is a complex polymer that provides strength and rigidity to the bacterial cell wall. It consists of alternating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), which are connected by short peptide chains. These peptide chains are cross-linked to form a 3D network, providing structural integrity to the cell wall.
One of the important steps in the synthesis of peptidoglycan is the cross-linking of the peptide chains. This process involves the formation of covalent bonds between the amino acid residues of adjacent peptide chains. The cross-linking reaction is catalyzed by enzymes called transpeptidases or penicillin-binding proteins (PBPs).
The reason why D-amino acids are present in the cross-links of peptidoglycan is that most peptidases, which are enzymes that break down peptides, can only cleave L-amino acids. By incorporating D-amino acids into the peptide chains, bacteria can protect the peptidoglycan layer from degradation by peptidases, making the cell wall more resistant to attack.
With the presence of D-amino acids in the cross-links, peptidases are unable to recognize and cleave these bonds effectively, thus maintaining the structural integrity of the peptidoglycan layer. This provides a selective advantage to bacteria by preventing the breakdown of their cell walls and enhancing their resistance against external threats.
Therefore, the most likely reason for the presence of D-amino acids in the cross-links of the peptidoglycan layer is to protect the cell wall from degradation by peptidases, as most peptidases can only cleave L-amino acids.