Novel type of murein transglycosylase in Escherichia coli

Abstract

The purification and properties of a novel type of murein transglycosylase from E. coli are described. The purified enzyme appears as a single band on sodium dodecyl sulfate polyacrylamide gels and has an apparent molecular weight of approximately 65,000 as estimated by gel filtration and gel electrophoresis. It degrades pure murein sacculi from E. coli almost completely into low molecular weight products. The two prominent muropeptide fragments in the digest are the disaccharide tripeptide N acetylglucosamine N acetylmuramic acid L alanine D iso glutamic acid meso diaminopimelic acid and the corresponding disaccharide tetrapeptide N acetylglucosamine N acetylmuramic acid L alanine D iso glutamic acid meso diaminopimelic acid D alanine. The unique feature of these compounds is that the disaccharide has no reducing end group and that the muramic acid residue possesses an internal 1→6 anhydro linkage. The new lytic enzyme is designated as a murein:murein transglycosylase. Its possible role in the rearrangement of murein during cell growth and division is discussed.