Bacterial AmpD at the Crossroads of Peptidoglycan Recycling and Manifestation of Antibiotic Resistance
摘要:
The bacterial, enzyme AmpD is an early catalyst in commitment of cell wall metabolites to the recycling events within the cytoplasm. The key internalized metabolite of Cell watt recycling, beta-D-N-acetytgtucosamine-(1 -> 4)-1,6-anhydro-beta-N-acetytmuramyl-L-Ala-gamma-D-Glu-meso-DAP-D-Ala-D-Ala (compound 1), is a poor substrate for AmpD. Two additional metabolites, 1,6-anhydro-N-acetyimuramyl-peptidyl derivatives 2a and 2c, served as substrates for AmpD with a k(cat)/K-m of >10(4) M-1 s(-1). The enzyme hydrolytically processes the lactyl amide bond of the 1,6-anhydro-N-acetylmuramyl moiety. The syntheses of these substrates and other ligands are reported herein, which made the characterization of the enzymic reaction possible. Furthermore, it is documented that the enzyme is specific for both the atypical peptide stem of the cell wall fragments and the presence of the sterically encumbered 1,6-anhydro-N-acetylmuramyl moiety; hence it is a peptidase with a unique function in bacterial. physiology. The implications of the function of this catalyst for the entry into the cell wall recycling events and the reversal of induction of the production of beta-lactamase, an antibiotic resistance determinant, are discussed.
A group of Gram-negative bacteria, including the problematic pathogen Pseudomonas aeruginosa, has linked the steps in cell-wall recycling with the ability to manifest resistance to beta-lactam antibiotics. A key step at the crossroads of the two events is performed by the protease AmpD, which hydrolyzes the peptide in the metabolite that influences these events. In contrast to other organisms that harbor this elaborate system, the genomic sequences of P. aeruginosa reveal it to have three paralogous genes for this protease, designated as ampD, ampDh2, and ampDh3. The recombinant gene products were purified to homogeneity, and their functions were assessed by the use of synthetic samples of three bacterial metabolites in cell-wall recycling and of three surrogates of cell-wall peptidoglycan. The results unequivocally identify AmpD as the bona fide recycling enzyme and AmpDh2 and AmpDh3 as enzymes involved in turnover of the bacterial cell wall itself. These findings define for the first time the events mediated by these three enzymes that lead to turnover of a key cell-wall recycling metabolite as well as the cell wall itself in its maturation.
Hesek, Dusan; Lee, Mijoon; Zhang, Weilie, Journal of the American Chemical Society, 2009, vol. 131, p. 5187 - 5193
作者:Hesek, Dusan、Lee, Mijoon、Zhang, Weilie、Noll, Bruce C.、Mobashery, Shahriar
DOI:——
日期:——
Bacterial AmpD at the Crossroads of Peptidoglycan Recycling and Manifestation of Antibiotic Resistance
作者:Mijoon Lee、Weilie Zhang、Dusan Hesek、Bruce C. Noll、Bill Boggess、Shahriar Mobashery
DOI:10.1021/ja9025566
日期:2009.7.1
The bacterial, enzyme AmpD is an early catalyst in commitment of cell wall metabolites to the recycling events within the cytoplasm. The key internalized metabolite of Cell watt recycling, beta-D-N-acetytgtucosamine-(1 -> 4)-1,6-anhydro-beta-N-acetytmuramyl-L-Ala-gamma-D-Glu-meso-DAP-D-Ala-D-Ala (compound 1), is a poor substrate for AmpD. Two additional metabolites, 1,6-anhydro-N-acetyimuramyl-peptidyl derivatives 2a and 2c, served as substrates for AmpD with a k(cat)/K-m of >10(4) M-1 s(-1). The enzyme hydrolytically processes the lactyl amide bond of the 1,6-anhydro-N-acetylmuramyl moiety. The syntheses of these substrates and other ligands are reported herein, which made the characterization of the enzymic reaction possible. Furthermore, it is documented that the enzyme is specific for both the atypical peptide stem of the cell wall fragments and the presence of the sterically encumbered 1,6-anhydro-N-acetylmuramyl moiety; hence it is a peptidase with a unique function in bacterial. physiology. The implications of the function of this catalyst for the entry into the cell wall recycling events and the reversal of induction of the production of beta-lactamase, an antibiotic resistance determinant, are discussed.