The role of gut microbial β-glucuronidase in drug disposition and development

Abstract

Gut microbial β-glucuronidase (gmGUS) is involved in the disposition of many endogenous and exogenous compounds. Preclinical studies have shown that inhibiting gmGUS activity affects drug disposition, resulting in reduced toxicity in the gastrointestinal tract (GIT) and enhanced systemic efficacy. Additionally, manipulating gmGUS activity is expected to be effective in preventing/treating local or systemic diseases. Although results from animal studies are promising, challenges remain in developing drugs by targeting gmGUS. Here, we review the role of gmGUS in host health under physiological and pathological conditions, the impact of gmGUS on the disposition of phenolic compounds, models used to study gmGUS activity, and the perspectives and challenges in developing drugs by targeting gmGUS.

Keywords: Drug development; Drug disposition; Druggable target; Gut microbial β-glucuronidase.

Figure 1.

Schematic representation of microbial β-glucuronidases (gmGUS) Pathophysiology. gmGUS plays critical role in the enterohepatic recycling of toxic substances (e.g, anticancer drugs, opioids, dietary carcinogens) and endogenous substrates (ENS) (e.g, estrogen, androgen, serotonin, bilirubin, and dopamine etc.). Elevated gmGUS activity due to dysbiosis of the gut microbiome associated with colon cancer, inflammatory bowel disease, and drug-induced intestinal injury led to increase systemic and gut levels of ENS and increase toxic compounds exposure to colonocytes and subsequent epithelial damage.

Figure 2.. Structure and sequence homology of GUS enzymes.

(A) Structure of E. coli GUS with an inhibitor, glucaro-D-lactam. This protein formed a homotetramer in the original X-ray crystal structure (PDB: 3K4D). A monomer is selected to illustrate the tertiary structure of this protein (left) and its active site (right). The parts illustrated as red and blue sticks represent the Loop 1 and Loop 2 regions, respectively. E. coli GUS belongs to the L1 subgroup and its Loop 1 region is proximate to the inhibitor molecule. Other colored parts in cartoon mode have ≥ 90% sequence identity among GUS homologs from a modified version of the HMGC279 GUS data set curated from the Human Microbiome Project (HMP) Stool Sample Catalog. Samples in the HMGC279 dataset that were described as fragments or had undetermined taxonomy were removed, resulting in a subset of 229 GUS enzyme amino acid sequences (GUS229) that we used for identifying conserved regions. Many of these conserved regions form the active site and interact with the inhibitor. (B) Amino acid sequence of E. coli GUS. Highlighted regions of this sequence (SRS017191.56930) correspond to the conserved motifs colorized in Figure 1A. Loop region sequences are outlined (Loop 1, blue; Loop 2, red). (C) Hierarchical clustering dendrogram of GUS homologs from the GUS229 dataset. Inter-motif regions containing Loop 1 and Loop 2 (from GUS229) were each aligned in UGENE (v41.0) using MUSCLE (with default parameters). A sequence identity distance matrix for the GUS229 alignment was calculated in R (v4.1.2) using the R package seqinr (v4.2–8) to evaluate sequence identity, and a custom Python (v3.9) script to weigh the length of the two loop regions. The aggregate distance matrix was used for agglomerative hierarchical clustering (“mcquitty” method) in R. Loop subgroups are distinguished by color as indicated on the dendrogram. Homologs from the same subgroup (L1, mL1,2, mL1, mL2, L2, and NL) clearly clustered together.

Figure 3.

HER, EER and Glucuronide Localization to the Lower Gut.