The Specificity Requirements of Bacteriophage T4 Lysozyme

Abstract

A series of bacterial cell wall glycopeptides of low molecular weight and cell wall nucleotide precursors have been tested for their inhibitory action on the digestion by T4 lysozyme of a radioactively labeled linear uncrosslinked peptidoglycan. The disaccharide‐peptides GlcNAc‐MurNAc‐l‐Ala‐d‐Glu(A₂pm) (C₅) and GlcNAc‐MurNAc‐l‐Ala‐d‐Glu(A₂pm‐d‐Ala) (C₆) as well as the monosaccharide‐peptide MurNAc‐l‐Ala‐d‐Glu(A₂pm) were found to be good competitive inhibitors (with similar K₁ values) whereas the disaccharide‐pentapeptide GIcNAcMurNAc‐l‐Ala‐d Glu‐Gly l‐Lys‐d‐Ala was a poor inhibitor. T4 lysozyme did not catalyse transglycosylation reactions from Escherichia coli B peptidoglycan to the disaccharide‐peptide C₆. No changes were seen in the circular dichroism spectra (200–250 nm) or fluorescence emission spectra upon binding of the good inhibitors. The results obtained indicate that T4 lysozyme has a small active site capable of recognizing a unit consisting of MurNAc‐l‐Ala‐d‐Glu(A₂pm).