A study of the composition and structure of the cell-wall mucopeptide of micrococcus lysodeikticus

Abstract

Cell wall preparations from Micrococcus lysodeikticus contain 2-acetamido-3-O-carboxy ethyl- 2-deoxyglucose (N-acetylmuramic-acid), 2-acetamido-2-deoxyglucose (N-acetyl-glucosamine), glutamate, lysine, glycine and alanine in the molecular proportions 0.81:1:1:1:2. This mucopeptide accounts for 85% of the wall. Approximately equimolar proportions of NH3, glucose and acetic-acid are present. Acid-base titration shows 16 moles/104 g of basic groups with pK of 10.5. The isoelectric point was 4.0. About half the e -amino-groups of lysine in the whole mucopeptide are possibly combined with a similar proportion of the [gamma] -carboxyl groups of glutamic-acid. The total titratable acidic and basic groups provide evidence for rather extensive cross-linking in the whole polymer.