Hydrolysis of soluble, linear, un-cross-linked peptidoglycans by endogenous bacterial N-acetylmuramoylhydrolases

J. F. Barrett, V. L. Schramm, G. D. Shockman

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Soluble, linear, uncross-linked peptidoglycans, prepared from two autolysis-defective mutants of Streptococcus faecium ATCC 9790 and from Micrococcus leuteus, were used as substrates for studies of hydrolysis by an N-acetylmuramoylhydrolase (muramidase). The kinetics of hydrolysis of these substrates and the ability of the muramidases isolated from S. faecium ATCC 9790 and from two autolysis-defective mutants, Lyt-14 and Aut-3, to carry out transglycosylation reactions were compared with the action of hen egg white lysozyme (EC 3.2.1.17). Hydrolysis of these substrates by the endogenous streptococcal muramidases resulted in the production of disaccharide-peptide monomers. As estimated from increases in reducing groups, hydrolysis proceeded at a linear rate for extended intervals, with consumption of up to 75% of the substrate, even at substrate concentrations well below the K(m) value. Apparent K(m) and relative V(max) values for the three streptococcal enzymes were indistinguishable from each other or from those for hen egg white lysozyme. These results indicate that the autolysis-defective phenotype of these mutants cannot be attributed to differences in their muramidases. In contrast to the action of hen egg white lysozyme, the streptococcal muramidase failed to catalyze transglycosylations. The extended periods of hydrolysis at constant rates are consistent with the occurrence of multiple catalytic events after the formation of the enzyme-substrate complex.

Original languageEnglish (US)
Pages (from-to)520-526
Number of pages7
JournalJournal of Bacteriology
Volume159
Issue number2
StatePublished - 1984
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

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