Alkaline Labile D-Alanine in Cell Walls

Abstract

EVIDENCE has been presented by Baddiley et al.¹that “in the native walls the teichoic acid has free phosphate and amino groups and is presumably held in the wall through ionic linkages and hydrogen bonds”. However, Strominger² has proposed, as an alternative, that the teichoic acid may be “attached to the glycopeptide through the peptide”. In this latter proposal the ester-linked D-alanine of the teichoic acid and the last peptide linked D-alanine of the mucopeptide would be the same alanine residue. Such a linkage would require that cold 5 or 10 per cent trichloroacetic acid, which has been used to remove teichoic acid from walls1, selectively hydrolyses the D-alanyl–D-alanine peptide bond, leaving the other peptide bonds present and the labile ester linkage unaffected. In addition, similarities in the molar ratios of amino-acids and muramic acid in cell walls and in the principal uridine nucleotide (Park compound) which accumulates under conditions of penicillin treatment of Staphylococcus aureus have been used in support of the role of this uridine muramic acid pentapeptide as a direct or nearly immediate precursor of the muramic acid peptide (mucopeptide) of the wall³.