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

Abstract

Possible conformations of X-D-alanyl⁴-D-alanine₅ and its analogs X-L-analyl₄-D-alanine₅ X-D-alanyl₄-L-alanine₅, X-D-butyl₄-D-alanine₅, X-D-alanyl₄-D-butyric acid₅, X-D-valyl₄-D-alanine₅, and X-D-alanyl₄-D-valine₅ 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.