Escherichia coli murein transglycosylase, a potential autolysin which splits the sugar chains of the murein sacculus, was rapidly purified from a crude cell extract by sequential chromatography on columns of blue Sepharose and poly(U)-Sepharose. In accordance with the binding to blue Sepharose and poly(U)-Sepharose, the transglycosylase is inhibited by Cibacron blue F3G-A, the affinity ligand of blue Sepharose, and also by polynucleotides, the latter, however, with varying efficiency. Among the polynucleotides tested, single-stranded DNA was found to be one of the most potent inhibitors. When bound to a blue Sepharose column, transglycosylase could be displaced from the column with single-stranded DNA. Taken together, these results point to a polynucleotide binding area on the transglycosylase molecule. Some aspects of the blue Sepharose affinity chromatography and the possible biological significance of the transglycosylase are discussed.