Importance of the two tryptophan residues in the Streptomyces R61 exocellular DD-peptidase

C. Bourguignon-Bellefroid, J. M. Wilkin, B. Joris, R. T. Aplin, C. Houssier, F. G. Prendergast, J. Van Beeumen, J. M. Ghuysen, J. M. Frere

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14 Scopus citations


Modification of the Streptomyces R61 DD-peptidase by N-bromosuccinimide resulted in a rapid loss of enzyme activity. In consequence, the role of the enzyme's two tryptophan residues was investigated by site-directed mutagenesis. Trp271 was replaced by Leu. The modification yielded a stable enzyme whose structural and catalytic properties were similar to those of the wild-type protein. Thus the Trp271 residue, though almost invariant among the β-lactamases of classes A and C and the low-M(r) penicillin-binding proteins, did not appear to be essential for enzyme activity. Mutations of the Trp233 into Leu and Ser strongly decreased the enzymic activity, the affinity for β-lactams and the protein stability. Surprisingly, the benzylpenicilloyl-(W233L)enzyme deacylated at least 300-fold more quickly than the corresponding acyl-enzyme formed with the wild-type protein and gave rise to benzylpenicilloate instead of phenylacetylglycine. This mutant peptidase thus behaved as a weak β-lactamase.

Original languageEnglish (US)
Pages (from-to)361-367
Number of pages7
JournalBiochemical Journal
Issue number2
StatePublished - 1992

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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