Theoretical studies on peptidoglycans. I. Effect of L‐alanyl, D‐butyl, or D‐valyl residuces at the positions 4 or 5 of the pentapeptide moiety of peptidoglycan on the cross‐linking reaction

Possible conformations of X‐ D ‐alanyl 4 ‐ D ‐alanine 5 and its analogs X‐ L ‐analyl 4 ‐ D ‐alanine 5 X‐ D ‐alanyl 4 ‐ L ‐alanine 5 , X‐ D ‐butyl 4 ‐ D ‐alanine 5 , X‐ D ‐alanyl 4 ‐ D ‐butyric acid 5 , X‐ D ‐valyl 4 ‐ D ‐alanine 5 , and X‐ D ‐alanyl 4 ‐ D ‐valine 5 have been analyzed by theoretical methods. These studies suggest that L ‐alanine and D ‐valine at the 4 or 5 postion of the pentapeptide moiety of peptidoglycan will drastically reduce the cross‐linking in peptidoglycan biosynthesis, whereas the effect of D ‐ butyric acid will be marked at the 4 postition and modeate at the 5 position. This is in good agreement with experimental results. The cross‐linking enzyme transpeptidase requires a specific confroamation for the 4th and 5th residues for optimal binding.