N-Leucinyl Benzenesulfonamides as Structurally Simplified Leucyl-tRNA Synthetase Inhibitors.

N-Leucinyl benzenesulfonamides have been discovered as a novel class of potent inhibitors of E. coli leucyl-tRNA synthetase. The binding of inhibitors to the enzyme was measured by using isothermal titration calorimetry. This provided information on enthalpy and entropy contributions to binding, which, together with docking studies, were used for structure-activity relationship analysis. Enzymatic assays revealed that N-leucinyl benzenesulfonamides display remarkable selectivity for E. coli leucyl-tRNA synthetase compared to S. aureus and human orthologues. The simplest analogue of the series, N-leucinyl benzenesulfonamide (R = H), showed the highest affinity against E. coli leucyl-tRNA synthetase and also exhibited antibacterial activity against Gram-negative pathogens (the best MIC = 8 µg/mL, E. coli ATCC 25922), which renders it as a promising template for antibacterial drug discovery.

Suppression of intestinal microbiota-dependent production of pro-atherogenic trimethylamine N-oxide by shifting L-carnitine microbial degradation.

AIMS: Trimethylamine-N-oxide (TMAO) is produced in host liver from trimethylamine (TMA). TMAO and TMA share common dietary quaternary amine precursors, carnitine and choline, which are metabolized by the intestinal microbiota. TMAO recently has been linked to the pathogenesis of atherosclerosis and severity of cardiovascular diseases. We examined the effects of anti-atherosclerotic compound meldonium, an aza-analogue of carnitine bioprecursor gamma-butyrobetaine (GBB), on the availability of TMA and TMAO. MAIN METHODS: Wistar rats received L-carnitine, GBB or choline alone or in combination with meldonium. Plasma, urine and rat small intestine perfusate samples were assayed for L-carnitine, GBB, choline and TMAO using UPLC-MS/MS. Meldonium effects on TMA production by intestinal bacteria from L-carnitine and choline were tested. KEY FINDINGS: Treatment with meldonium significantly decreased intestinal microbiota-dependent production of TMA/TMAO from L-carnitine, but not from choline. 24hours after the administration of meldonium, the urinary excretion of TMAO was 3.6 times lower in the combination group than in the L-carnitine-alone group. In addition, the administration of meldonium together with L-carnitine significantly increased GBB concentration in blood plasma and in isolated rat small intestine perfusate. Meldonium did not influence bacterial growth and bacterial uptake of L-carnitine, but TMA production by the intestinal microbiota bacteria K. pneumoniae was significantly decreased. SIGNIFICANCE: We have shown for the first time that TMA/TMAO production from quaternary amines could be decreased by targeting bacterial TMA-production. In addition, the production of pro-atherogenic TMAO can be suppressed by shifting the microbial degradation pattern of supplemental/dietary quaternary amines.

Targeting carnitine biosynthesis: discovery of new inhibitors against γ-butyrobetaine hydroxylase.

γ-Butyrobetaine hydroxylase (BBOX) catalyzes the conversion of gamma butyrobetaine (GBB) to l-carnitine, which is involved in the generation of metabolic energy from long-chain fatty acids. BBOX inhibitor 3-(1,1,1-trimethylhydrazin-1-ium-2-yl)propanoate (mildronate), which is an approved, clinically used cardioprotective drug, is a relatively poor BBOX inhibitor and requires high daily doses. In this paper we describe the design, synthesis, and properties of 51 compounds, which include both GBB and mildronate analogues. We have discovered novel BBOX inhibitors with improved IC50 values; the best examples are in the nanomolar range and about 2 orders of magnitude better when compared to mildronate. For six inhibitors, crystal structures in complex with BBOX have been solved to explain their activities and pave the way for further inhibitor design.