Identification of potential antivirulence agents by substitution-oriented screening for inhibitors of Streptococcus pyogenes sortase A.

Antimicrobial resistance resulting in ineffective treatment of infectious diseases is an increasing global problem, particularly in infections with pathogenic bacteria. In some bacteria, such as Streptococcus pyogenes, the pathogenicity is strongly linked to the attachment of virulence factors. Their attachment to the cellular membrane is a transpeptidation reaction, catalyzed by sortase enzymes. As such, sortases pose an interesting target for the development of new antivirulence strategies that could yield novel antimicrobial drugs. Using the substitution-oriented fragment screening (SOS) approach, we discovered a potent and specific inhibitor (C10) of sortase A from S. pyogenes. The inhibitor C10 showed high specificity towards S. pyogenes sortase A, with an IC50 value of 10 µM and a Kd of 60 µM. We envision that this inhibitor could be employed as a starting point for further exploration of sortase's potential as therapeutic target for antimicrobial drug development.

Rational Development of a Potent 15-Lipoxygenase-1 Inhibitor with in Vitro and ex Vivo Anti-inflammatory Properties.

Human 15-lipoxygenase-1 (h-15-LOX-1) is a mammalian lipoxygenase and plays an important role in several inflammatory lung diseases such as asthma, COPD, and chronic bronchitis. Novel potent inhibitors of h-15-LOX-1 are required to explore the role of this enzyme further and to enable drug discovery efforts. In this study, we applied an approach in which we screened a fragment collection that is focused on a diverse substitution pattern of nitrogen-containing heterocycles such as indoles, quinolones, pyrazoles, and others. We denoted this approach substitution-oriented fragment screening (SOS) because it focuses on the identification of novel substitution patterns rather than on novel scaffolds. This approach enabled the identification of hits with good potency and clear structure-activity relationships (SAR) for h-1-5-LOX-1 inhibition. Molecular modeling enabled the rationalization of the observed SAR and supported structure-based design for further optimization to obtain inhibitor 14 d that binds with a Ki of 36 nM to the enzyme. In vitro and ex vivo biological evaluations of our best inhibitor demonstrate a significant increase of interleukin-10 (IL-10) gene expression, which indicates its anti-inflammatory properties.

Metabolic alkene labeling and in vitro detection of histone acylation via the aqueous oxidative Heck reaction.

The detection of protein lysine acylations remains a challenge due to lack of specific antibodies for acylations with various chain lengths. This problem can be addressed by metabolic labeling techniques using carboxylates with reactive functionalities. Subsequent chemoselective reactions with a complementary moiety connected to a detection tag enable the visualization and quantification of the protein lysine acylome. In this study, we present EDTA-Pd(II) as a novel catalyst for the oxidative Heck reaction on protein-bound alkenes, which allows employment of fully aqueous reaction conditions. We used this reaction to monitor histone lysine acylation in vitro after metabolic incorporation of olefinic carboxylates as chemical reporters.

Anacardic acid derived salicylates are inhibitors or activators of lipoxygenases.

Lipoxygenases catalyze the oxidation of unsaturated fatty acids, such as linoleic acid, which play a crucial role in inflammatory responses. Selective inhibitors may provide a new therapeutic approach for inflammatory diseases. In this study, we describe the identification of a novel soybean lipoxygenase-1 (SLO-1) inhibitor and a potato 5-lipoxygenase (5-LOX) activator from a screening of a focused compound collection around the natural product anacardic acid. The natural product anacardic acid inhibits SLO-1 with an IC(50) of 52 µM, whereas the inhibitory potency of the novel mixed type inhibitor 23 is fivefold enhanced. In addition, another derivative (21) caused non-essential activation of potato 5-LOX. This suggests the presence of an allosteric binding site that regulates the lipoxygenase activity.