Biosynthesis of Drug Glucuronide Metabolites in the Budding Yeast Saccharomyces cerevisiae

The binding selectivity of quercetin and its structure-related polyphenols to human serum albumin using a fluorescent dye cocktail for multiplex drug-site mapping

Human serum albumin (HSA) is a serum protein that carries flavonoids in blood circulation. In this report, the binding selectivity and strength of interactions to HSA-binding sites (sites I or II) by flavonoids were evaluated using competition experiments and the specific fluorescent dyes, dansylamide and BD140. Most tested flavonoids bound site I preferentially, with the binding strength dependent on the mother structure in the order flavonol > flavone > flavanone > flavan 3-ols. Glycosylation or glucuronidation reduced the binding of quercetin to site I of HSA, whereas sulfation increased binding. Quercetin 7-sulfate showed the strongest binding and molecular docking simulations supported this observation. Prenylation at any position or glucuronidation and sulfation at the C-4' or C-7 position of quercetin facilitated stronger binding to site II. The binding affinity of flavonoids toward site I correlated with the partition coefficient value (logP), whereas no corresponding correlation was observed for site II.

Comparison of metabolism and biological properties among positional isomers of quercetin glucuronide in LPS- and RANKL-challenged RAW264.7 cells

The major quercetin metabolite, quercetin-3-glucuronide, exerts various biological activities, including anti-inflammatory effects. This study aimed to evaluate the metabolic profiles and biological properties of the positional isomers of quercetin monoglucuronides (Q3G, Q7G, Q3'G, and Q4'G) in activated macrophages. In addition to quercetin aglycone, Q7G was more cytotoxic than the other quercetin monoglucuronides (QGs), which corresponded to its lower stability under neutral pH conditions. Q3G was most effective in inhibiting both LPS-dependent induction of IL-6 and RANKL-dependent activation of tartrate-resistant acid phosphatase; however, Q3'G and Q4'G may also help exert biological activities without potential cytotoxicity. The deconjugation efficacy to generate quercetin aglycone differed among QGs, with the highest efficacy in Q3G. These results suggest that the chemical or biological properties and metabolic profiles may depend on the stability of QGs to generate quercetin aglycone using β-glucuronidase.

Complete Reaction Phenotyping of Propranolol and 4-Hydroxypropranolol with the 19 Enzymes of the Human UGT1 and UGT2 Families

Propranolol is a competitive non-selective beta-receptor antagonist that is available on the market as a racemic mixture. In the present study, glucuronidation of propranolol and its equipotent phase I metabolite 4-hydroxypropranolol by all 19 members of the human UGT1 and UGT2 families was monitored. UGT1A7, UGT1A9, UGT1A10 and UGT2A1 were found to glucuronidate propranolol, with UGT1A7, UGT1A9 and UGT2A1 mainly acting on (S)-propranolol, while UGT1A10 displays the opposite stereoselectivity. UGT1A7, UGT1A9 and UGT2A1 were also found to glucuronidate 4-hydroxypropranolol. In contrast to propranolol, 4-hydroxypropranolol was found to be glucuronidated by UGT1A8 but not by UGT1A10. Additional biotransformations with 4-methoxypropanolol demonstrated different regioselectivities of these UGTs with respect to the aliphatic and aromatic hydroxy groups of the substrate. Modeling and molecular docking studies were performed to explain the stereoselective glucuronidation of the substrates under study.

8-Prenylnaringenin tissue distribution and pharmacokinetics in mice and its binding to human serum albumin and cellular uptake in human embryonic kidney cells

8-Prenylnaringenin (8-PN), a hop flavonoid, is a promising food substance with health benefits. Compared with nonprenylated naringenin, 8-PN exhibits stronger estrogenic activity and prevents muscle atrophy. Moreover, 8-PN prevents hot flushes and bone loss. Considering that prenylation reportedly improves the bioavailability of flavonoids, we compared the parameters related to the bioavailability [pharmacokinetics and tissue distribution in C57/BL6 mice, binding affinity to human serum albumin (HSA), and cellular uptake in HEK293 cells] of 8-PN and its mother (non-prenylated) compound naringenin. C57/BL6 mice were fed an 8-PN or naringenin mixed diet for 22 days. The amount of 8-PN (nmol/g tissue) in the kidneys (16.8 ± 9.20), liver (14.8 ± 2.58), muscles (3.33 ± 0.60), lungs (2.07 ± 0.68), pancreas (1.80 ± 0.38), heart (1.71 ± 0.27), spleen (1.36 ± 0.29), and brain (0.31 ± 0.09) was higher than that of naringenin. A pharmacokinetic study in mice demonstrated that the C _max of 8-PN (50 mg/kg body weight) was lower than that of naringenin; however, the plasma concentration of 8-PN 8 h after ingestion was higher than that of naringenin. The binding affinity of 8-PN to HSA and cellular uptake in HEK293 cells were higher than those of naringenin. 8-PN bioavailability features assessed in mouse or human model experiments were obviously different from those of naringenin.

Heteroconjugates of quercetin with 4'-O-sulfate selectively accumulate in rat plasma due to limited urinary excretion

Quercetin and methylquercetin are present in a variety of sulfate and glucuronide conjugates in the plasma of quercetin-fed rats and humans. Quercetin conjugates exhibit various physiological activities, depending on the type and position of conjugation. However, little is known regarding the type and position of isomers of quercetin conjugates in the plasma, their accumulation in the liver and kidneys, and their excretion via urine. Using authentic standards of quercetin conjugates and liquid chromatography-tandem mass spectrometry (LC/MS/MS) analysis, we identified and quantified various quercetin conjugates in blood plasma, urine, liver, and kidney tissues 1, 4, and 10 h after orally administering 33.1 μmol kg^-1 quercetin glucosides to rats. The profiles of quercetin conjugates were largely different among plasma, urine, liver, and kidneys. Very limited heteroconjugates (7-O-glucuronide-4'-O-sulfate) of quercetin and methylquercetin dominated in the plasma, but these heteroconjugates were much less excreted via urine and did not largely accumulate in the liver and kidneys. Heteroconjugates constituting sulfates other than 4' position sulfate, 7-O-glucuronide-3'-O-sulfate, 4'-O-glucuronide-7-O-sulfate, and 3'-O-glucuronide-7-O-sulfate were major metabolites in urine, but were minimally detected in the plasma. We also found that mono-sulfate conjugates were abundant in the liver and renal tissues. These results suggest that excretion of quercetin conjugates, especially heteroconjugates, into urine is highly selective. The heteroconjugates with 4'-O-sulfate may be scarcely excreted via urine, and thus accumulate in the blood plasma. Further research is necessary to evaluate the physiological effects of heteroconjugates accumulated in the plasma.

Pharmacokinetics and metabolism of cinnamic acid derivatives and flavonoids after oral administration of Brazilian green propolis in humans

Brazilian green propolis (BGP) has chemical compounds from botanical origin that are mainly cinnamic acid derivatives (artepillin C, baccharin, and drupanin) and flavonoids (kaempferide and 6-methoxykaempferide). These compounds are expected to play an important role in the pharmacological activities of BGP. However, there is little known about the pharmacokinetics and metabolism of these compounds after oral administration of BGP. The aim of this study is to investigate the pharmacokinetics and metabolism of BGP components in humans. Twelve volunteers received 3 capsules containing 360 mg of BGP ethanol extract powder. Plasma samples were collected before and up to 24 h after the intake of BGP capsules. The collected plasma samples with or without hydrolysis by the deconjugating enzyme were analyzed by LC/MS/MS. After enzymatic hydrolysis, the C_max values of artepillin C and drupanin, which were detected mainly in plasma after ingestion of BGP capsules, were 1255 ± 517 and 2893 ± 711 nM, respectively, of which 89.3% and 88.2% were found to be the phenolic glucuronide conjugate. This is the first time that the pharmacokinetics of the BGP components of human metabolites have been reported. Our results could provide useful information for the design and interpretation of studies to investigate the mechanisms and pharmacological effects of BGP.

A SET domain-containing protein involved in cell wall integrity signaling and peroxisome biogenesis is essential for appressorium formation and pathogenicity of Colletotrichum gloeosporioides

The chromatin modulator Set5 plays important regulatory roles in both cell growth and stress responses of Saccharomyces cerevisiae. However, its function in filamentous fungi remains poorly understood. Here, we report the pathogenicity-related gene CgSET5 discovered in a T-DNA insertional mutant M285 of Colletotrichum gloeosporioides. Bioinformatic analysis revealed that CgSET5 encodes a SET domain-containing protein that is a homolog of the budding yeast S. cerevisiae Set5. CgSET5 is important for hyphae growth and conidiation and is necessary for appressorium formation and pathogenicity. CgSet5 regulates appressorium formation in a mitogen-activated protein kinase-independent manner. Inactivation of CgSET5 resulted in a significant reduction in chitin content within the cell wall, indicating CgSet5 plays a vital role in cell wall integrity. CgSet5 is involved in peroxisome biogenesis. We identified CgSet5 as the histone H4 methyltransferase, which methylates the critical H4 lysine residues 5 and 8 in C. gloeosporioides. We carried out a yeast two-hybrid screen to find CgSet5 interacting partners. We found CgSet5 putatively interacts with an inorganic pyrophosphatase named CgPpa1, which co-localized in the cytoplasm with CgSet5. Finally, CgPpa1 was found to strongly interact with CgSet5 in vivo during appressorium formation by bimolecular fluorescence complementation assays. These data corroborate a complex control function of CgSet5 acting as a core pathogenic regulator, which connects cell wall integrity and peroxisome biogenesis in C. gloeosporioides.

Whole-cell dependent biosynthesis of N- and S-oxides using human flavin containing monooxygenases expressing budding yeast

Flavin containing monooxygenases (FMOs) represent one of the predominant types of phase I drug metabolizing enzymes (DMEs), and thus play an important role in the metabolism of xeno- and endobiotics for the generation of their corresponding oxides. These oxides often display biological activities, however they are difficult to study since their chemical or biological synthesis is generally challenging even though only small amounts are required to evaluate their efficacy and safety. Previously, we constructed a DME expression system for cytochrome P450, UDP-glucuronosyltransferase (UGT), and sulfotransferase (SULT) using yeast cells, and successfully produced xenobiotic metabolites in a whole-cell dependent manner. In this study, we developed a heterologous expression system for human FMOs, including FMO1-FMO5, in Saccharomyces cerevisiae and examined its N- and S-oxide productivity. The recombinant yeast cells expressed each of the FMO successfully, and the FMO4 transformant produced N- and S-oxide metabolites at several milligrams per liter within 24 h. This whole-cell dependent biosynthesis enabled the production of N- and S-oxides without the use of the expensive cofactor NADPH. Such novel yeast expression system could be a powerful tool for the production of oxide metabolites.

Dynamics of the Cellular Metabolism of Leptosperin Found in Manuka Honey

Leptosperin (methyl syringate β-d-gentiobioside) is abundantly found in manuka honey, which is widely used because of its antibacterial and possible anti-inflammatory activities. The aim of this study was to examine the molecular mechanism underlying the metabolism of leptosperin. Five phytochemicals (leptosperin, methyl syringate (MSYR), glucuronate conjugate of MSYR (MSYR-GA), sulfonate conjugate of MSYR (MSYR-S), and syringic acid (SYR)) were separately incubated with HepG2 and Caco-2 cells. After incubation, we found that the concentration of MSYR decreased, whereas the concentrations of SYR, MSYR-GA, and MSYR-S increased. By profiling with inhibitors and carboxylesterases (CES1, 2), we found that the conversion from MSYR to SYR was mediated by CES1. Lipopolysaccharide-stimulated RAW264.7 cells restored MSYR-GA to MSYR possibly by the secreted β-glucuronidase. All of the mice administered with leptosperin, MSYR, or manuka honey showed higher MSYR (13.84 ± 11.51, 14.29 ± 9.19, or 6.66 ± 2.30 nM) and SYR (1.85 ± 0.66, 6.01 ± 1.20, or 8.16 ± 3.10 nM) levels in the plasma compared with that of the vehicle controls (3.33 ± 1.45 (MSYR) and 1.85 ± 0.66 (SYR) nM). The findings of our study indicate that the unique metabolic pathways of these compounds may account for possible functionalities of manuka honey.

Comprehensive Analyses of Quercetin Conjugates by LC/MS/MS Revealed That Isorhamnetin-7- O-glucuronide-4'- O-sulfate Is a Major Metabolite in Plasma of Rats Fed with Quercetin Glucosides

Quercetin glycosides in the diet are absorbed and converted to glucuronides, sulfates, or mixed conjugates of glucuronide and sulfate in plasma. Physiological effects of quercetin conjugates (Q-conjugates) differ depending on the type and position of conjugation. We developed a comprehensive analysis of Q-conjugates, including mixed conjugates, by LC/MS/MS. The whole species of Q-conjugates in tail blood plasma was measured on days 1, 3, and 12 in rats fed a 0.24% quercetin glucoside-containing diet. Twenty-three Q-conjugate molecules were detected, and 16 Q-conjugates among these were quantified using standard compounds. The most abundant metabolite in the plasma was mixed conjugates, comprising isorhamnetin-7- O-glucuronide-4'- O-sulfate, followed by quercetin-7- O-glucuronide-4'- O-sulfate; together, they accounted for 86% of total Q-conjugates on day 12. The profile of quercetin conjugate species did not significantly change during 12 days. The total Q-conjugate molecules quantified by our method was comparable with the total Q-conjugates quantified using an enzymatic deconjugation method.

Synthesis of steroid bisglucuronide and sulfate glucuronide reference materials: Unearthing neglected treasures of steroid metabolism

Doubly or bisconjugated steroid metabolites have long been known as minor components of the steroid profile that have traditionally been studied by laborious and indirect fractionation, hydrolysis and gas chromatography-mass spectrometry (GC-MS) analysis. Recently, the synthesis and characterisation of steroid bis(sulfate) (aka disulfate or bis-sulfate) reference materials enabled the liquid chromatography-tandem mass spectrometry (LC-MS/MS) study of this metabolite class and the development of a constant ion loss (CIL) scan method for the direct and untargeted detection of steroid bis(sulfate) metabolites. Methods for the direct LC-MS/MS detection of other bisconjugated steroids, such as steroid bisglucuronide and mixed steroid sulfate glucuronide metabolites, have great potential to reveal a more complete picture of the steroid profile. However, access to steroid bisglucuronide or sulfate glucuronide reference materials necessary for LC-MS/MS method development, metabolite identification or quantification is severely limited. In this work, ten steroid bisglucuronide and ten steroid sulfate glucuronide reference materials were synthesised through an ordered combination of chemical sulfation and/or enzymatic glucuronylation reactions. All compounds were purified and characterised using NMR and MS methods. Chemistry for the preparation of stable isotope labelled steroid {¹³C₆}-glucuronide internal standards has also been developed and applied to the preparation of two selectively mono-labelled steroid bisglucuronide reference materials used to characterise more completely MS fragmentation pathways. The electrospray ionisation and fragmentation of the bisconjugated steroid reference materials has been studied. Preliminary targeted ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analysis of the reference materials prepared revealed the presence of three steroid sulfate glucuronides as endogenous human urinary metabolites.

Practical one-step glucuronidation via biotransformation

We herein report a practical one-step glucuronidation method by biotransformation using Streptomyces sp. SANK 60895. This novel direct method of biotransformation has been shown to be more practical and scalable for glucuronidation than previously reported chemical and enzymatic procedures given its simplicity, high β-selectivity, cost-effectiveness, and reproducibility. We applied the present method to the synthesis of acyl glucuronide and hydroxy-β-glucuronide of mycophenolic acid and compound 4, respectively. This method was also shown to be applicable to the N-glucuronidation of various compounds.

Human Enzymes for Organic Synthesis

Human enzymes have been widely studied in various disciplines. The number of reactions taking place in the human body is vast, and so is the number of potential catalysts for synthesis. Herein, we focus on the application of human enzymes that catalyze chemical reactions in course of the metabolism of drugs and xenobiotics. Some of these reactions have been explored on the preparative scale. The major field of application of human enzymes is currently drug development, where they are applied for the synthesis of drug metabolites.

Simultaneous collection of the portal and superior vena cava blood in conscious rats defined that intestinal epithelium is the major site of glucuronidation, but not sulfation and methylation, of quercetin

Quercetin is a flavonoid with many physiological effects. Absorbed quercetin is rapidly conjugated in the intestinal epithelium and liver. Different positional isomers of quercetin conjugates have different physiological properties. However, the mechanisms of quercetin conjugation in the intestine are not fully clarified. We examined the regioselective quercetin conjugate formation in the intestine after oral administration of quercetin glycosides, by simultaneous sampling of blood from the portal vein and superior vena cava, and quantifying various positional isomers of quercetin glucuronides and sulfates in conscious rats. Concentrations of quercetin glucuronides were higher in blood from the portal vein than the superior vena cava, showing that glucuronidation mainly occurred in the intestine. Such differences were not observed for quercetin sulfates. Regioselectivity of the intestinal glucuronidation in quercetin hydroxyl groups were 7- >3'- >3- >4'-OH. Quercetin was mainly sulfated on 3'-OH at 30 min, but on 4'-OH at 240 min.

Metabolic engineering of glycosylated polyketide biosynthesis

Microbial cell factories are extensively used for the biosynthesis of value-added chemicals, biopharmaceuticals, and biofuels. Microbial biosynthesis is also realistic for the production of heterologous molecules including complex natural products of plant and microbial origin. Glycosylation is a well-known post-modification method to engineer sugar-functionalized natural products. It is of particular interest to chemical biologists to increase chemical diversity of molecules. Employing the state-of-the-art systems and synthetic biology tools, a range of small to complex glycosylated natural products have been produced from microbes using a simple and sustainable fermentation approach. In this context, this review covers recent notable metabolic engineering approaches used for the biosynthesis of glycosylated plant and microbial polyketides in different microorganisms. This review article is broadly divided into two major parts. The first part is focused on the biosynthesis of glycosylated plant polyketides in prokaryotes and yeast cells, while the second part is focused on the generation of glycosylated microbial polyketides in actinomycetes.

Flavonoid metabolism: the interaction of metabolites and gut microbiota

Several dietary flavonoids exhibit anti-oxidative, anti-inflammatory, and anti-osteoporotic activities relevant to prevention of chronic diseases, including lifestyle-related diseases. Dietary flavonoids (glycoside forms) are enzymatically hydrolyzed and absorbed in the intestine, and are conjugated to their glucuronide/sulfate forms by phase II enzymes in epithelial cells and the liver. The intestinal microbiota plays an important role in the metabolism of flavonoids found in foods. Some specific products of bacterial transformation, such as ring-fission products and reduced metabolites, exhibit enhanced properties. Studies on the metabolism of flavonoids by the intestinal microbiota are crucial for understanding the role of these compounds and their impact on our health. This review focused on the metabolic pathways, bioavailability, and physiological role of flavonoids, especially metabolites of quercetin and isoflavone produced by the intestinal microbiota.

Whole-cell-dependent biosynthesis of sulfo-conjugate using human sulfotransferase expressing budding yeast

Cytosolic sulfotransferases (SULTs), one of the predominant phase II drug metabolizing enzymes (DME), play important roles in metabolism of xeno- and endobiotics to generate their sulfo-conjugates. These sulfo-conjugates often have biological activities but are difficult to study, because even though only small amounts are required to evaluate their efficacy and safety, chemical or biological synthesis of sulfo-conjugatesis is often challenging. Previously, we constructed a DME expression system for cytochrome P450 and UGT, using yeast cells, and successfully produced xenobiotic metabolites in a whole-cell-dependent manner. In this study, we developed a yeast expression system for human SULTs, including SULT1A1, 1A3, 1B1, 1C4, 1E1, and 2A1, in Saccharomyces cerevisiae and examined its sulfo-conjugate productivity. The recombinant yeast cells expressing each of the SULTs successfully produced several hundred milligram per liter of xeno- or endobioticsulfo-conjugates within 6 h. This whole-cell-dependent biosynthesis enabled us to produce sulfo-conjugates without the use of 3'-phosphoadenosine-5'-phosphosulfate, an expensive cofactor. Additionally, the production of regiospecific sulfo-conjugates of several polyphenols was possible with this method, making this novel yeast expression system a powerful tool for uncovering the metabolic pathways and biological actions of sulfo-conjugates.