Article (Scientific journals)
The pH dependence of the active-site serine DD-peptidase of Streptomyces R61
Varetto, Louis; Frère, Jean-Marie; Nguyen-Distèche, Martine et al.
1987In European Journal of Biochemistry, 162 (3), p. 525-531
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Keywords :
acylation; anti-bacterial agents/pharmacology; binding sites/drug effects; carboxypeptidases/antagonists & inhibitors/*metabolism; hydrogen-ion concentration; hydrolysis; kinetics; lactams; models, chemical; oligopeptides/metabolism; serine-type d-ala-d-ala carboxypeptidase; streptomyces/*enzymology
Abstract :
[en] Titration of the active-site serine DD-peptidase of Streptomyces R61 shows that formation of acyl enzyme during hydrolysis of the substrate Ac2-L-Lys-D-Ala-D-Ala and enzyme inactivation by the beta-lactam compounds benzylpenicillin, N-acetylampicillin and ampicillin relies on the acidic form of an enzyme's group of pK approximately equal to 9.5. It is proposed that protonation of a lysine epsilon-amino group facilitates initial binding by charge pairing with the free carboxylate of the substrate and the beta-lactam molecules. Lowering the pH from 7 to 5 has no effect on the second-order rate constant of enzyme acylation by benzylpenicillin and N-acetylampicillin but results in a decreased rate constant of acylation by ampicillin and Ac2-L-Lys-D-Ala-D-Ala. Protonation of the side-chain amino group of ampicillin and a decreased efficacy of the initial binding of the peptide to the enzyme seem to be responsible for the observed effects. Whatever the molecule bound to the enzyme, there is no sign for the active involvement of an enzyme's histidine residue of pK 6.5-7.0 in the hydrolysis pathway.
Disciplines :
Microbiology
Biochemistry, biophysics & molecular biology
Author, co-author :
Varetto, Louis;  Université de Liège - ULiège > Institut de Chimie > Service de Microbiologie
Frère, Jean-Marie ;  Université de Liège - ULiège > Institut de Chimie > Service de Microbiologie
Nguyen-Distèche, Martine ;  Université de Liège - ULiège > Institut de Chimie > Service de Microbiologie
Ghuysen, Jean-Marie ;  Université de Liège - ULiège > Institut de Chimie > Service de Microbiologie
Houssier, Claude ;  Université de Liège - ULiège > Institut de Chimie > Laboratoire de Chimie macromoléculaire et Chimie physique
Language :
English
Title :
The pH dependence of the active-site serine DD-peptidase of Streptomyces R61
Publication date :
02 February 1987
Journal title :
European Journal of Biochemistry
ISSN :
0014-2956
eISSN :
1432-1033
Publisher :
Blackwell Science, Oxford, United Kingdom
Volume :
162
Issue :
3
Pages :
525-531
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 07 January 2011

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