Covalent modification of the β-1,4-N-acetylmuramoylhydrolase of Streptococcus faecium with 5-mercaptouridine monophosphate

Purified β-1,4-N-acetylmuramoylhydrolase (muramidase-1; EC 3.2.1.17) of Streptococcus faecium ATCC 9790 has been shown to be covalently substituted with ≃12 mol equivalents of monomeric 5-mercaptouridine monophosphate. All 12 residues are present on the proteolytically processed 87-kDa active form of the enzyme. A peptide fragment containing 5-mercaptouridine, tyrosine, alanine, glycine, and leucine was isolated consistent with an O-phosphate linkage of the nucleotide to tyrosine.