A widely distributed metalloenzyme class enables gut microbial metabolism of host- and diet-derived catechols

Abstract

17Catechol dehydroxylation is a central chemical transformation in the gut microbial 18 metabolism of plant-and host-derived small molecules. However, the molecular basis for this 19 transformation and its distribution among gut microorganisms are poorly understood. Here, we 20 characterize a molybdenum-dependent enzyme from the prevalent human gut bacterium 21Eggerthella lenta that specifically dehydroxylates catecholamine neurotransmitters available in 22 the human gut. Our findings suggest that this activity enables E. lenta to use dopamine as an 23 electron acceptor under anaerobic conditions. In addition to characterizing catecholamine 24 dehydroxylation, we identify candidate molybdenum-dependent enzymes that dehydroxylate 25 additional host-and plant-derived small molecules. These gut bacterial catechol dehydroxylases 26 are specific in their substrate scope and transcriptional regulation and belong to a distinct group of 27 range of compounds that includes dietary phytochemicals, host neurotransmitters, clinically used 51 drugs, and microbial siderophores (14-16) ( Fig. 1A). Discovered over six decades ago, catechol 52 dehydroxylation is a uniquely microbial reaction that selectively replaces the para hydroxyl group 53 of the catechol with a hydrogen atom (17) (Fig. 1A). This reaction is particularly challenging due 54 to the stability of the aromatic ring system. Prominent substrates for microbial dehydroxylation 55 include the drug fostamatinib (18), the catecholamine neurotransmitters norepinephrine and 56 dopamine (19,20), and the phytochemicals ellagic acid (found in nuts and berries), caffeic acid (a 57 universal lignin precursor in plants), and catechin (present in chocolate and tea) (21-23) ( Fig. 1B). 58Dehydroxylation alters the bioactivity of the catechol compound (24, 25) and produces metabolites 59 that act both locally in the gut and systemically to influence human health and disease (18,(25)(26)(27)(28)(29)(30). 60However, the gut microbial enzymes responsible for catechol dehydroxylation have remained 61 largely unknown. 62We recently reported the discovery of a catechol dehydroxylating enzyme from the 63 prevalent human gut Actinobacterium Eggerthella lenta. This enzyme participates in an 64 interspecies gut microbial pathway that degrades the Parkinson's disease medication L-dopa by 65 catalyzing the regioselective p-dehydroxylation of dopamine to m-tyramine (29). To identify the 66 enzyme, we grew E. lenta strain A2 with and without dopamine and used RNA sequencing (RNA-67 seq) to find genes induced by dopamine. Only 15 genes were significantly upregulated in the 68 presence of dopamine, including a putative molybdenum-dependent enzyme that was induced 69 >2500 fold. Hypothesizing this gene encoded the dopamine dehydroxylase, we purified the 70 enzyme from E. lenta and confirmed its activity in vitro. Dopamine dehydroxylase (Dadh) is 71 predicted to bind bis-molybdopterin guanine nucleotide (bis-MGD), a complex metallocofactor 72 that contains a catalytically essential molybdenum atom (...

Genetic manipulation of the human gut bacterium Eggerthella lenta reveals a widespread family of transcriptional regulators

“…Eggerthella species are also associated with several chronic human diseases, including asthma 4 , renal disease 5 , multiple sclerosis 6 , and rheumatoid arthritis 7 , although a causal role for Eggerthella in these disorders has not yet been established. E. lenta and related human gut Coriobacteriia also perform a wide variety of metabolic transformations, including inactivation of the widely used cardiac drug digoxin 8 , 9 , various reactions of dietary phytochemicals 10 , 11 , dehydroxylation of catechols 12 , 13 , and metabolism of bile acids 14 , 15 . Gaining a mechanistic understanding of these metabolic activities and their regulation in a host setting could better inform efforts to modulate gut microbial activities to improve human health.…”

“…The interactions of E. lenta and closely related Gordonibacter species with catechols (compounds containing a 1,2-dihydroxylated aromatic ring) highlight intriguing fundamental questions. These gut organisms use a recently discovered class of molybdenum-dependent enzymes to catalyze the chemically challenging removal of a hydroxyl group from catechol substrates 12 . This dehydroxylation reaction occurs on a wide range of catechols in the human gut, including dietary phytochemicals and host neurotransmitters, likely altering their bioactivity and bioavailability.…”

Human gut Actinobacteria boost drug absorption by secreting P-glycoprotein ATPase inhibitors

“…Notably, two genes predictive of P-gp inhibition were found within the same genomic locus and annotated as impacting molybdate transport: modA (molybdate-binding protein) and modB (molybdenum transport system permease protein; Figures 4B,C ). This suggests molybdate, a redox-active metal that complexes with diverse bacterial enzymes (Zhong, Kobe, and Kappler 2020; Maini Rekdal et al 2020), is important for the biosynthetic pathways that Coriobacteriia use to produce the P-gp inhibitors.…”

“…Among these 7 genes were modA and modB , two genes involved in molybdenum transport (Rech, Wolin, and Gunsalus 1996). Molybdenum, redox-active under physiological conditions, forms an active site for many bacterial enzymes involved in diverse redox chemistry (Maini Rekdal et al 2019; Bess et al 2020; Hille 1996; Maini Rekdal et al 2020), potentially including isoflavonoid biosynthesis.…”

“…This suggests molybdate, a redox-active metal that complexes with diverse bacterial enzymes (Zhong, Kobe, and Kappler 2020;Maini Rekdal et al 2020), is important for the biosynthetic pathways that Coriobacteriia use to produce the P-gp inhibitors.…”