Beta-glucuronidase (bacterial) (GUS)

Bacterial beta-glucuronidases are glycoside hydrolase enzymes produced by gut microbiota that catalyze the removal of glucuronic acid from glucuronidated compounds.[1][2][3] These enzymes play a critical role in the microbial metabolism of both endogenous compounds and xenobiotics, effectively reversing phase II drug conjugation performed by host liver enzymes.[3] The bacterial GUS enzyme family exhibits remarkable structural diversity—even within single bacterial species like *Bacteroides uniformis*, multiple structurally and functionally distinct GUS enzymes with different substrate specificities can exist.[2] This diversity has important clinical implications: bacterial GUS activity can reactivate drug metabolites in the intestine, modulating drug efficacy and toxicity, particularly for compounds like the cancer therapeutic irinotecan.[2] Selective inhibition of bacterial GUS enzymes represents a potential therapeutic strategy to prevent unwanted drug reactivation and reduce associated toxicities, though the structural plasticity and diversity of these enzymes presents a challenge for developing broad-spectrum inhibitors.[1]

Other names

Bacterial β-glucuronidaseMicrobial glucuronidaseLoop-β-glucuronidases (L-GUS)No-loop β-glucuronidases (NL-GUS)GUS enzymes (general term for bacterial variants)

Catalytic hydrolysis: removes glucuronic acid from glucuronidated substrates through glycosidic bond cleavage Active site mechanism involving catalytic glutamate and lysine residues that recognize the glucuronic acid carboxylate Substrate specificity varies among different bacterial GUS enzymes based on active site architecture