Terbium(III) Luminescence-Based Assay for Esterase Activity.

Esterases catalyze the hydrolysis of esters to form a carboxylic acid and alcohol. These enzymes play a key role in both the detoxification of xenobiotic compounds and the metabolism of drugs and prodrugs. Numerous fluorogenic probes have been developed to monitor esterase activity. Most are based on an aromatic alcohol, and the others are based on an aromatic acid. These restrictions leave unexplored the specificity of esterases for aliphatic esters. Here, we report on the use of esters of thiopheneacetic acid coupled with the luminescence of terbium(III) as the basis for a continuous assay of esterase activity. This probe allows for a wide variation of the alcohol moiety and the detection of its hydrolysis at submicromolar concentrations. The assay verifies steady-state kinetic parameters for catalysis by pig liver esterase from either initial rates or the integration of progress curves, and its utility is evident with unpurified esterases in bacterial and human cell lysates.

Targeting the human gut microbiome with small-molecule inhibitors.

The human gut microbiome is a complex microbial community that is strongly linked to both host health and disease. However, the detailed molecular mechanisms underlying the effects of these microorganisms on host biology remain largely uncharacterized. The development of non-lethal, small-molecule inhibitors that target specific gut microbial activities enables a powerful but underutilized approach to studying the gut microbiome and a promising therapeutic strategy. In this Review, we will discuss the challenges of studying this microbial community, the historic use of small-molecule inhibitors in microbial ecology, and recent applications of this strategy. We also discuss the evidence suggesting that host-targeted drugs can affect the growth and metabolism of gut microbes. Finally, we address the issues of developing and implementing microbiome-targeted small-molecule inhibitors and define important future directions for this research.

Endogenous Enzymes Enable Antimicrobial Activity.

In light of the continued threat of antimicrobial-resistant bacteria, new strategies to expand the repertoire of antimicrobial compounds are necessary. Prodrugs are an underexploited strategy in this effort. Here, we report on the enhanced antimicrobial activity of a prodrug toward bacteria having an enzyme capable of its activation. A screen led us to the sulfurol ester of the antibiotic trans-3-(4-chlorobenzoyl)acrylic acid. An endogenous esterase makes Mycolycibacterium smegmatis sensitive to this prodrug. Candidate esterases were identified, and their heterologous production made Escherichia coli sensitive to the ester prodrug. Taken together, these data suggest a new approach to the development of antimicrobial compounds that takes advantage of endogenous enzymatic activities to target specific bacteria.