Peptidoglycan biosynthesis in Escherichia coli: variations in the metabolism of alanine and D-alanyl-D-alanine.
The in vivo functioning of the alanine/D-alanyl-D-alanine pathway of Escherichia coli was investigated by determining precursor pool levels and specific enzyme activities under various growth conditions. Cells grown on D- or L-alanine showed several remarkable features compared with cells grown on other carbon sources: 10-fold higher values of the D-alanyl-D-alanine and the UDP-MurNAc-pentapeptide pools, a 240-fold increase of the alanine racemase activity, and the absence of bacteriolysis after treatment with D-cycloserine at high concentrations (50 micrograms ml-1). In cells grown on glucose, D-cycloserine (1 micrograms ml-1) led to depletion of the D-alanyl-D-alanine pool and to lysis, which was efficiently antagonized by chloramphenicol. A threefold increase of the dipeptide pool was observed when cells were treated with chloramphenicol alone. The alanine racemase activity was lowest in glucose-grown cells and the D-alanine:D-alanine ligase and D-alanyl-D-alanine-adding activities were the same whatever the carbon source. Molecular masses of 53-56 kDa and 56-60 kDa were estimated for the partially purified inducible alanine racemase and D-alanine:D-alanine ligase respectively.
de Roubin
M R
MR
Unité de Recherche Associée 1131 du CNRS, Biochimie Moléculaire et Cellulaire, Université Paris-Sud, Orsay, France.
Mengin-Lecreulx
D
D
van Heijenoort
J
J
D000409:Alanine / Q000378:metabolism*; D002701:Chloramphenicol / Q000494:pharmacology; D003523:Cycloserine / Q000494:pharmacology; D004151:Dipeptides / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D007700:Kinetics; D010457:Peptidoglycan / Q000096:biosynthesis*
D004151:Dipeptides; D010457:Peptidoglycan; C002956:alanylalanine; D002701:Chloramphenicol; D003523:Cycloserine; D000409:Alanine