Article (Scientific journals)
Dual substrate specificity of Bacillus subtilis PBP4a
Nemmara, Venkatesh V.; Adediran, S. A.; Dave, Kinjal et al.
2013In Biochemistry, 52, p. 2627-2637
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Keywords :
enzymology; Low molecular mass PBP; Bacillus subtilis
Abstract :
[en] Bacterial DD-peptidases are the targets of the β-lactam antibiotics. The sharp increase in bacterial resistance toward these antibiotics in recent years has stimulated the search for non- β-lactam alternatives. The substrates of DD-peptidases are elements of peptidoglycan from bacterial cell walls. Attempts to base DD-peptidase inhibitor design on peptidoglycan structure, however, have not been particularly successful to date because the specific substrates for most of these enzymes are unknown. It is known, however, that the preferred substrates of low-molecular mass (LMM) class B and C DD-peptidases contain the free N-terminus of the relevant peptidoglycan. Two very similar LMMC enzymes, for example, the Actinomadura R39 DD-peptidase and Bacillus subtilis PBP4a, recognize a D-α-aminopimelyl terminus. The peptidoglycan of B. subtilis in the vegetative stage, however, has the N-terminal D-α-aminopimelyl carboxylic acid amidated. The question is, therefore, whether the DD-peptidases of B. subtilis are separately specific to carboxylate or carboxamide or have dual specificity. This paper describes an investigation of this issue with B. subtilis PBP4a. This enzyme was indeed found to have a dual specificity for peptide substrates, both in the acyl donor and in the acyl acceptor sites. In contrast, the R39 DD-peptidase, from an organism in which the peptidoglycan is not amidated, has a strong preference for a terminal carboxylate. It was also found that acyl acceptors, reacting with acyl−enzyme intermediates, were preferentially D-amino acid amides for PBP4a and the corresponding amino acids for the R39 DD-peptidase. Examination of the relevant crystal structures, aided by molecular modeling, suggested that the expansion of specificity in PBP4a accompanies a change of Arg351 in the R39 enzyme and most LMMC DD-peptidases to histidine in PBP4a and its orthologs in other Bacillus sp. This histidine, in neutral form at pH 7, appeared to be able to favorably interact with both carboxylate and carboxamide termini of substrates, in agreement with the kinetic data. It may still be possible, in specific cases, to combat bacteria with new antibiotics based on particular elements of their peptidoglycan structure.
Disciplines :
Microbiology
Author, co-author :
Nemmara, Venkatesh V.;  Wesleyan university, connecticut 06459, USA > Department of chemistry
Adediran, S. A.;  Wesleyan university, Connecticut 06459, USA > Department of chemistry
Dave, Kinjal;  Wesleyan university, Connecticut 06459, USA > department of chemistry
Duez, Colette ;  Université de Liège > Centre d'ingénierie des protéines
Pratt, Rex F.;  Wesleyan university, Connecticut 06459, USA > Department of chemistry
Language :
English
Title :
Dual substrate specificity of Bacillus subtilis PBP4a
Publication date :
05 April 2013
Journal title :
Biochemistry
ISSN :
0006-2960
eISSN :
1520-4995
Publisher :
American Chemical Society, Washington, United States - District of Columbia
Volume :
52
Pages :
2627-2637
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 04 September 2015

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