Gut microbial ß-glucuronidases influence endobiotic homeostasis and are modulated by diverse therapeutics.

Hormones and neurotransmitters are essential to homeostasis, and their disruptions are connected to diseases ranging from cancer to anxiety. The differential reactivation of endobiotic glucuronides by gut microbial ß-glucuronidase (GUS) enzymes may influence interindividual differences in the onset and treatment of disease. Using multi-omic, in vitro, and in vivo approaches, we show that germ-free mice have reduced levels of active endobiotics and that distinct gut microbial Loop 1 and FMN GUS enzymes drive hormone and neurotransmitter reactivation. We demonstrate that a range of FDA-approved drugs prevent this reactivation by intercepting the catalytic cycle of the enzymes in a conserved fashion. Finally, we find that inhibiting GUS in conventional mice reduces free serotonin and increases its inactive glucuronide in the serum and intestines. Our results illuminate the indispensability of gut microbial enzymes in sustaining endobiotic homeostasis and indicate that therapeutic disruptions of this metabolism promote interindividual response variabilities.

Mechanism-based inhibition of gut microbial tryptophanases reduces serum indoxyl sulfate.

Indoxyl sulfate is a microbially derived uremic toxin that accumulates in late-stage chronic kidney disease and contributes to both renal and cardiovascular toxicity. Indoxyl sulfate is generated by the metabolism of indole, a compound created solely by gut microbial tryptophanases. Here, we characterize the landscape of tryptophanase enzymes in the human gut microbiome and find remarkable structural and functional similarities across diverse taxa. We leverage this homology through a medicinal chemistry campaign to create a potent pan-inhibitor, (3S) ALG-05, and validate its action as a transition-state analog. (3S) ALG-05 successfully reduces indole production in microbial culture and displays minimal toxicity against microbial and mammalian cells. Mice treated with (3S) ALG-05 show reduced cecal indole and serum indoxyl sulfate levels with minimal changes in other tryptophan-metabolizing pathways. These studies present a non-bactericidal pan-inhibitor of gut microbial tryptophanases with potential promise for reducing indoxyl sulfate in chronic kidney disease.

Dried Protein Structure Revealed at the Residue Level by Liquid-Observed Vapor Exchange NMR.

Water is key to protein structure and stability, yet the relationship between protein-water interactions and structure is poorly understood, in part because there are few techniques that permit the study of dehydrated protein structure at high resolution. Here, we describe liquid-observed vapor exchange (LOVE) NMR, a solution NMR-based method that provides residue-level information about the structure of dehydrated proteins. Using the model protein GB1, we show that LOVE NMR measurements reflect the fraction of the dried protein population trapped in a conformation where a given residue is protected from exchange with D2O vapor. Comparisons to solution hydrogen-deuterium exchange data affirm that the dried protein structure is strongly influenced by local solution stability and that the mechanism of dehydration protection exerted by the widely used protectant trehalose differs from its mechanism of stabilization in solution. Our results highlight the need for refined models of cosolute-mediated dehydration protection and demonstrate the ability of LOVE NMR to inform such models.