Cover image for Vol. 15 Issue 6

Editor: Peter Gölitz

Online ISSN: 1439-7633

Associated Title(s): ChemCatChem, ChemMedChem, ChemPhysChem, ChemSusChem

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January 30, 2014

Very Important Papers:

Active Efflux Influences the Potency of Quorum-Sensing Inhibitors in Pseudomonas aeruginosa

Joseph D. Moore, Joseph P. Gerdt, Nora R. Eibergen, and Helen E. Blackwell*

Small molecules capable of inhibiting bacterial cell--cell signaling, or quorum sensing (QS), are of significant interest as new chemical tools and potential anti-infective agents. Gram-negative bacteria predominately use N-acyl L-homoserine lactone (AHL) signals for QS. Now, Helen E. Blackwell (University of Wisconsin) and co-workers have shown that a variety of AHL-derived QS inhibitors in the pathogen Pseudomonas aeruginosa are substrates of its MexAB-OprM drug-efflux pump. In contrast, an aminobenzimidazole-type QS inhibitor does not display this efflux-induced reduction in potency. These results suggest that active efflux will need to be considered in the design of new QS modulators in P. aeruginosa and other bacteria.

Catalytic Scope of the Thiamine-Dependent Multifunctional Enzyme Cyclohexane-1,2-dione Hydrolase

Sabrina Loschonsky, Simon Waltzer, Sonja Fraas, Tobias Wacker, Susana L. A. Andrade, Peter M. H. Kroneck, and Michael Müller*

Cyclohexane-1,2-dione hydrolase (CDH) is a thiamine diphosphate-dependent enzyme that can accept a number of aromatic aldehydes that were previously hard to convert. Now, Michael Müller (Universität Freiburg) and co-workers have expressed CDH in E. coli and the recombinant CDH showed the same C–C bond-cleavage and C–C bond-formation activities as the wild-type enzyme. Furthermore, CDH catalyzes the asymmetric cross-benzoin reaction of aromatic aldehydes and pyruvate, up to quantitative conversion and 92–99% ee. On a semipreparative scale, the sterically demanding substrates 4-(tert-butyl)benzaldehyde and 2-naphthaldehyde, respectively, were transformed into the corresponding 2-hydroxyketone products in high yields. Additionally, certain benzaldehydes with electron-withdrawing substituents were identified as potential inhibitors of the C–C bond-formation activity of CDH. In a related paper, published simultaneously in ChemCatChem, M. Müller and co-workers also characterized the ability of CDH to catalyze the enantio-selective formation of (S)-acetoin by homocoupling of pyruvate, homocoupling of acetaldehyde, and cross-coupling of pyruvate and acetaldehyde.

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