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Santulli G, Kansakar U, Varzideh F, Mone P, Jankauskas SS, Lombardi A. Functional Role of Taurine in Aging and Cardiovascular Health: An Updated Overview. Nutrients 2023; 15:4236. [PMID: 37836520 PMCID: PMC10574552 DOI: 10.3390/nu15194236] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 09/22/2023] [Accepted: 09/27/2023] [Indexed: 10/15/2023] Open
Abstract
Taurine, a naturally occurring sulfur-containing amino acid, has attracted significant attention in recent years due to its potential health benefits. Found in various foods and often used in energy drinks and supplements, taurine has been studied extensively to understand its impact on human physiology. Determining its exact functional roles represents a complex and multifaceted topic. We provide an overview of the scientific literature and present an analysis of the effects of taurine on various aspects of human health, focusing on aging and cardiovascular pathophysiology, but also including athletic performance, metabolic regulation, and neurological function. Additionally, our report summarizes the current recommendations for taurine intake and addresses potential safety concerns. Evidence from both human and animal studies indicates that taurine may have beneficial cardiovascular effects, including blood pressure regulation, improved cardiac fitness, and enhanced vascular health. Its mechanisms of action and antioxidant properties make it also an intriguing candidate for potential anti-aging strategies.
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Affiliation(s)
- Gaetano Santulli
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism (FIDAM), Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA; (U.K.); (S.S.J.); (A.L.)
- Department of Molecular Pharmacology, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, New York, NY 10461, USA; (F.V.); (P.M.)
| | - Urna Kansakar
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism (FIDAM), Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA; (U.K.); (S.S.J.); (A.L.)
| | - Fahimeh Varzideh
- Department of Molecular Pharmacology, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, New York, NY 10461, USA; (F.V.); (P.M.)
| | - Pasquale Mone
- Department of Molecular Pharmacology, Division of Cardiology, Wilf Family Cardiovascular Research Institute, Albert Einstein College of Medicine, New York, NY 10461, USA; (F.V.); (P.M.)
| | - Stanislovas S. Jankauskas
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism (FIDAM), Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA; (U.K.); (S.S.J.); (A.L.)
| | - Angela Lombardi
- Department of Medicine, Fleischer Institute for Diabetes and Metabolism (FIDAM), Einstein-Mount Sinai Diabetes Research Center (ES-DRC), Einstein Institute for Aging Research, Albert Einstein College of Medicine, New York, NY 10461, USA; (U.K.); (S.S.J.); (A.L.)
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Furukawa T, Fukuda A. Maternal taurine as a modulator of Cl - homeostasis as well as of glycine/GABA A receptors for neocortical development. Front Cell Neurosci 2023; 17:1221441. [PMID: 37601283 PMCID: PMC10435090 DOI: 10.3389/fncel.2023.1221441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Accepted: 07/20/2023] [Indexed: 08/22/2023] Open
Abstract
During brain and spinal cord development, GABA and glycine, the inhibitory neurotransmitters, cause depolarization instead of hyperpolarization in adults. Since glycine and GABAA receptors (GABAARs) are chloride (Cl-) ion channel receptor, the conversion of GABA/glycine actions during development is influenced by changes in the transmembrane Cl- gradient, which is regulated by Cl- transporters, NKCC1 (absorption) and KCC2 (expulsion). In immature neurons, inhibitory neurotransmitters are released in a non-vesicular/non-synaptic manner, transitioning to vesicular/synaptic release as the neuron matures. In other word, in immature neurons, neurotransmitters generally act tonically. Thus, the glycine/GABA system is a developmentally multimodal system that is required for neurogenesis, differentiation, migration, and synaptogenesis. The endogenous agonists for these receptors are not fully understood, we address taurine. In this review, we will discuss about the properties and function of taurine during development of neocortex. Taurine cannot be synthesized by fetuses or neonates, and is transferred from maternal blood through the placenta or maternal milk ingestion. In developing neocortex, taurine level is higher than GABA level, and taurine tonically activates GABAARs to control radial migration as a stop signal. In the marginal zone (MZ) of the developing neocortex, endogenous taurine modulates the spread of excitatory synaptic transmission, activating glycine receptors (GlyRs) as an endogenous agonist. Thus, taurine affects information processing and crucial developmental processes such as axonal growth, cell migration, and lamination in the developing cerebral cortex. Additionally, we also refer to the possible mechanism of taurine-regulating Cl- homeostasis. External taurine is uptake by taurine transporter (TauT) and regulates NKCC1 and KCC2 mediated by intracellular signaling pathway, with-no-lysine kinase 1 (WNK1) and its subsequent kinases STE20/SPS1-related proline-alanine-rich protein kinase (SPAK) and oxidative stress response kinase-1 (OSR1). Through the regulation of NKCC1 and KCC2, mediated by the WNK-SPAK/OSR1 signaling pathway, taurine plays a role in maintaining Cl- homeostasis during normal brain development.
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Affiliation(s)
- Tomonori Furukawa
- Department of Neurophysiology, Hirosaki University Graduate School of Medicine, Hirosaki, Japan
| | - Atsuo Fukuda
- Department of Neurophysiology, Hamamatsu University School of Medicine, Hamamatsu, Japan
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3
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Walker A, Schmitt-Kopplin P. The role of fecal sulfur metabolome in inflammatory bowel diseases. Int J Med Microbiol 2021; 311:151513. [PMID: 34147944 DOI: 10.1016/j.ijmm.2021.151513] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 04/22/2021] [Accepted: 05/17/2021] [Indexed: 12/17/2022] Open
Abstract
Sulfur metabolism and sulfur-containing metabolites play an important role in the human digestive system, and sulfur compounds and pathways are associated with inflammatory bowel diseases (IBD). In fact, cysteine metabolism results in the production of taurine and sulfate, and gut microbes catabolize them into hydrogen sulfide, a signaling molecule with various biological functions. Besides metabolites originating from sulfur metabolism, several other sulfur-containing metabolites of different classes were detected in human feces, consisting of non-volatile and volatile compounds. Sulfated steroids and bile acids such as taurine-conjugated bile acids are the major classes along with sulfur amino acids and sulfur-containing peptides. Indeed, sulfur-containing metabolites were described in stool samples from healthy subjects, patients suffering from colorectal cancer or IBD. In metabolomics-driven studies, around 50 known sulfur-containing metabolites were linked to IBD. Taurine, taurocholic acid, taurochenodeoxycholic acid, methionine, methanethiol and hydrogen sulfide were regularly reported in IBD studies, and most of them were elevated in stool samples from IBD patients. We summarized from this review that there is strong interplay between perturbed gut microbiota in IBD, and the consistently higher abundance of sulfur-containing metabolites, which potentially represent substrates for sulfidogenic bacteria such as Bilophila or Escherichia and promote their growth. These bacteria might shift their metabolism towards the degradation of taurine and cysteine and therefore to a higher hydrogen sulfide production.
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Affiliation(s)
- Alesia Walker
- Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, Neuherberg, Germany.
| | - Philippe Schmitt-Kopplin
- Research Unit Analytical BioGeoChemistry, Helmholtz Zentrum München, Neuherberg, Germany; ZIEL Institute for Food and Health, Technical University of Munich, Freising, Germany; Chair of Analytical Food Chemistry, Technical University of Munich, Freising, Germany
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4
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Kang YP, Mockabee-Macias A, Jiang C, Falzone A, Prieto-Farigua N, Stone E, Harris IS, DeNicola GM. Non-canonical Glutamate-Cysteine Ligase Activity Protects against Ferroptosis. Cell Metab 2021; 33:174-189.e7. [PMID: 33357455 PMCID: PMC7839835 DOI: 10.1016/j.cmet.2020.12.007] [Citation(s) in RCA: 166] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Revised: 10/09/2020] [Accepted: 12/08/2020] [Indexed: 02/06/2023]
Abstract
Cysteine is required for maintaining cellular redox homeostasis in both normal and transformed cells. Deprivation of cysteine induces the iron-dependent form of cell death known as ferroptosis; however, the metabolic consequences of cysteine starvation beyond impairment of glutathione synthesis are poorly characterized. Here, we find that cystine starvation of non-small-cell lung cancer cell lines induces an unexpected accumulation of γ-glutamyl-peptides, which are produced due to a non-canonical activity of glutamate-cysteine ligase catalytic subunit (GCLC). This activity is enriched in cell lines with high levels of NRF2, a key transcriptional regulator of GCLC, but is also inducible in healthy murine tissues following cysteine limitation. γ-glutamyl-peptide synthesis limits the accumulation of glutamate, thereby protecting against ferroptosis. These results indicate that GCLC has a glutathione-independent, non-canonical role in the protection against ferroptosis by maintaining glutamate homeostasis under cystine starvation.
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Affiliation(s)
- Yun Pyo Kang
- Department of Cancer Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL 33612, USA
| | | | - Chang Jiang
- Department of Cancer Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL 33612, USA
| | - Aimee Falzone
- Department of Cancer Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL 33612, USA
| | | | - Everett Stone
- Department of Molecular Biosciences, University of Texas at Austin, Austin, TX 78712, USA
| | - Isaac S Harris
- University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Gina M DeNicola
- Department of Cancer Physiology, H. Lee. Moffitt Cancer Center, Tampa, FL 33612, USA.
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The role of glutamate oxaloacetate transaminases in sulfite biosynthesis and H 2S metabolism. Redox Biol 2020; 38:101800. [PMID: 33271457 PMCID: PMC7711302 DOI: 10.1016/j.redox.2020.101800] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 11/06/2020] [Accepted: 11/12/2020] [Indexed: 01/24/2023] Open
Abstract
Molybdenum cofactor deficiency and isolated sulfite oxidase deficiency are two rare genetic disorders that are caused by impairment of the mitochondrial enzyme sulfite oxidase. Sulfite oxidase is catalyzing the terminal reaction of cellular cysteine catabolism, the oxidation of sulfite to sulfate. Absence of sulfite oxidase leads to the accumulation of sulfite, which has been identified as a cellular toxin. However, the molecular pathways leading to the production of sulfite are still not completely understood. In order to identify novel treatment options for both disorders, the understanding of cellular cysteine catabolism – and its alterations upon loss of sulfite oxidase – is of utmost importance. Here we applied a new detection method of sulfite in cellular extracts to dissect the contribution of cytosolic and mitochondrial glutamate oxaloacetate transaminase (GOT) in the transformation of cysteine sulfinic acid to sulfite and pyruvate. We found that the cytosolic isoform GOT1 is primarily responsible for the production of sulfite. Moreover, loss of sulfite oxidase activity results in the accumulation of sulfite, H2S and persulfidated cysteine and glutathione, which is consistent with an increase of SQR protein levels. Surprisingly, none of the known H2S-producing pathways were found to be upregulated under conditions of sulfite toxicity suggesting an alternative route of sulfite-induced shift from oxidative to H2S dependent cysteine catabolism. Cellular sulfite detection enables investigation of cysteine catabolism in cell extracts. Cytosolic glutamate oxaloacetate transaminase 1 is the primary source for cellular sulfite. Deficiency of sulfite oxidase leads to accumulation of H2S and persulfidated small molecules. Sulfite oxidase deficiency results in a downregulation of H2S synthesis and increased SQR expression.
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Rakhshandeh A, de Lange CFM, Htoo JK, Rakhshandeh AR. Immune system stimulation increases the irreversible loss of cysteine to taurine, but not sulfate, in starter pigs. J Anim Sci 2020; 98:5698019. [PMID: 31909792 DOI: 10.1093/jas/skaa001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Accepted: 01/04/2020] [Indexed: 01/29/2023] Open
Abstract
An isotope tracer study was conducted to evaluate the effects of immune system stimulation (ISS) on the irreversible loss of cysteine (Cys) to taurine (Tau) and sulfate (SO4), as well as glutathione (GSH) synthesis, during the fed state in pigs. We previously have reported that ISS increases plasma Cys flux and the GSH synthesis rate at the tissue and whole-body levels in growing pigs. Thus, the current article presents the data on the irreversible loss of Cys during ISS in pigs. Ten gilts (BW: 7.0 ± 0.12 kg) were feed restricted a sulfur amino acids (SAA) limiting diet and injected twice with either saline (n = 4) or increasing amounts of E. coli lipopolysaccharide (n = 6). The day after the second injection, a 5-h primed continuous intravenous infusion of 35S-Cys was conducted. ISS reduced plasma Cys and total SAA concentrations (16% and 21%, respectively; P < 0.05). However, ISS had no effect on the plasma concentrations of Tau and SO4, nor did it affect the appearance of 35S in plasma Tau, plasma SO4, urinary Tau, or urinary SO4 (P > 0.19). On a whole-body basis and including urinary excretion, ISS increased the appearance of 35S in Tau by 67% (P < 0.05), but tended to decrease the appearance of 35S in SO4 by 22% (P < 0.09). Overall, the current findings indicate that during ISS, decreased plasma SAA concentrations and increased plasma Cys flux are attributed in part to increased rates of Cys conversion to Tau, but not Cys catabolism to SO4. Thus, increased utilization of Cys for the synthesis of immune system metabolites, such as GSH and Tau, is likely the main contributor to increased Cys flux during ISS in pigs. In addition, the irreversible loss of Cys during ISS is small and has a minimal impact on the daily SAA requirements of starter pigs.
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Affiliation(s)
- Anoosh Rakhshandeh
- Department of Animal and Food Science, Texas Tech University, Lubbock, TX, Canada.,Department of Animal Biosciences, University of Guelph, Guelph, ON, Canada
| | | | - John K Htoo
- Evonik Nutrition & Care GmbH, Rodenbacher Chaussee, Hanau, Germany
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Kushkevych I, Cejnar J, Treml J, Dordević D, Kollar P, Vítězová M. Recent Advances in Metabolic Pathways of Sulfate Reduction in Intestinal Bacteria. Cells 2020; 9:E698. [PMID: 32178484 PMCID: PMC7140700 DOI: 10.3390/cells9030698] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 01/10/2023] Open
Abstract
Sulfate is present in foods, beverages, and drinking water. Its reduction and concentration in the gut depend on the intestinal microbiome activity, especially sulfate-reducing bacteria (SRB), which can be involved in inflammatory bowel disease (IBD). Assimilatory sulfate reduction (ASR) is present in all living organisms. In this process, sulfate is reduced to hydrogen sulfide and then included in cysteine and methionine biosynthesis. In contrast to assimilatory sulfate reduction, the dissimilatory process is typical for SRB. A terminal product of this metabolism pathway is hydrogen sulfide, which can be involved in gut inflammation and also causes problems in industries (due to corrosion effects). The aim of the review was to compare assimilatory and dissimilatory sulfate reduction (DSR). These processes occur in some species of intestinal bacteria (e.g., Escherichia and Desulfovibrio genera). The main attention was focused on the description of genes and their location in selected strains. Their coding expression of the enzymes is associated with anabolic processes in various intestinal bacteria. These analyzed recent advances can be important factors for proposing possibilities of metabolic pathway extension from hydrogen sulfide to cysteine in intestinal SRB. The switch from the DSR metabolic pathway to the ASR metabolic pathway is important since toxic sulfide is not produced as a final product.
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Affiliation(s)
- Ivan Kushkevych
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 62500 Brno, Czech Republic; (J.C.); (M.V.)
- Department of Molecular Biology and Pharmaceutical Biotechnology, University of Veterinary and Pharmaceutical Sciences Brno, 61242 Brno, Czech Republic;
| | - Jiří Cejnar
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 62500 Brno, Czech Republic; (J.C.); (M.V.)
| | - Jakub Treml
- Department of Molecular Biology and Pharmaceutical Biotechnology, University of Veterinary and Pharmaceutical Sciences Brno, 61242 Brno, Czech Republic;
| | - Dani Dordević
- Department of Plant Origin Foodstuffs Hygiene and Technology, Faculty of Veterinary Hygiene and Ecology, University of Veterinary and Pharmaceutical Sciences, 61242 Brno, Czech Republic;
| | - Peter Kollar
- Department of Human Pharmacology and Toxicology, Faculty of Pharmacy, University of Veterinary and Pharmaceutical Sciences, 61242 Brno, Czech Republic;
| | - Monika Vítězová
- Department of Experimental Biology, Faculty of Science, Masaryk University, Kamenice 753/5, 62500 Brno, Czech Republic; (J.C.); (M.V.)
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Kang YP, Torrente L, Falzone A, Elkins CM, Liu M, Asara JM, Dibble CC, DeNicola GM. Cysteine dioxygenase 1 is a metabolic liability for non-small cell lung cancer. eLife 2019; 8:45572. [PMID: 31107239 PMCID: PMC6584702 DOI: 10.7554/elife.45572] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Accepted: 05/17/2019] [Indexed: 12/14/2022] Open
Abstract
NRF2 is emerging as a major regulator of cellular metabolism. However, most studies have been performed in cancer cells, where co-occurring mutations and tumor selective pressures complicate the influence of NRF2 on metabolism. Here we use genetically engineered, non-transformed primary murine cells to isolate the most immediate effects of NRF2 on cellular metabolism. We find that NRF2 promotes the accumulation of intracellular cysteine and engages the cysteine homeostatic control mechanism mediated by cysteine dioxygenase 1 (CDO1), which catalyzes the irreversible metabolism of cysteine to cysteine sulfinic acid (CSA). Notably, CDO1 is preferentially silenced by promoter methylation in human non-small cell lung cancers (NSCLC) harboring mutations in KEAP1, the negative regulator of NRF2. CDO1 silencing promotes proliferation of NSCLC by limiting the futile metabolism of cysteine to the wasteful and toxic byproducts CSA and sulfite (SO32-), and depletion of cellular NADPH. Thus, CDO1 is a metabolic liability for NSCLC cells with high intracellular cysteine, particularly NRF2/KEAP1 mutant cells. Cancers form in humans and other animals when cells of the body develop mutations that allow them to grow and divide uncontrollably. The set of chemical reactions happening inside cancer cells, referred to as “metabolism”, can be very different to metabolism in the healthy cells they originate from. Some of these differences are directly caused by mutations, while others are a result of the environment surrounding the cancer cells as they develop into a tumor. A protein called NRF2 is often overactive in human tumors due to mutations in its inhibitor protein KEAP1. Previous studies have shown that NRF2 changes the metabolism of cancer cells by switching specific genes on or off. However, since cancer cells also have other mutations that could mask or amplify some of the effects of NRF2, the precise role of this protein in metabolism remains unclear. To address this question, Kang et al. generated mice that could switch between producing the normal KEAP1 protein or a mutant version that is unable to inhibit NRF2. The mouse model was then used to examine the immediate effects of activating the NRF2 protein. This revealed that NRF2 altered how mouse cells used a molecule called cysteine, which is required to make proteins and other cell components. When NRF2 was active, some of the cysteine molecules were converted into two wasteful and toxic particles by an enzyme called CDO1. Kang et al. found that inactivating CDO1 in human lung cancer cells prevented these wasteful particles from being produced. This allows cancer cells to grow more rapidly, and may explain why human tumors generally evolve to shut down CDO1. The findings of Kang et al. show that not all of the changes in metabolism caused by individual mutations in cancer cells help tumors to grow. As a tumor develops it may need to acquire further mutations to override the negative effects of these changes in metabolism. In the future these findings may help researchers develop new therapies that reactivate or mimic CDO1 to limit the growth of tumors.
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Affiliation(s)
- Yun Pyo Kang
- Department of Cancer Physiology, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
| | - Laura Torrente
- Department of Cancer Physiology, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
| | - Aimee Falzone
- Department of Cancer Physiology, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
| | - Cody M Elkins
- Department of Cancer Physiology, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
| | - Min Liu
- Proteomics and Metabolomics Core Facility, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
| | - John M Asara
- Division of Signal Transduction, Beth Israel Deaconess Medical Center, Boston, United States.,Department of Medicine, Harvard Medical School, Boston, United States
| | - Christian C Dibble
- Department of Pathology and Cancer Center, Beth Israel Deaconess Medical Center, Boston, United States.,Department of Pathology, Harvard Medical School, Boston, United States
| | - Gina M DeNicola
- Department of Cancer Physiology, H Lee Moffitt Cancer Center and Research Institute, Tampa, United States
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Roberts JC. Stereoisomers of cysteine and its analogs Potential effects on chemo- and radioprotection strategies. Amino Acids 2013; 8:113-24. [PMID: 24186322 DOI: 10.1007/bf00806486] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/1994] [Accepted: 11/03/1994] [Indexed: 12/12/2022]
Abstract
The thiol-containing amino acid, cysteine, and its analogs are useful for a variety of protective applications, including protecting normal tissues against the unwanted side effects of cancer chemotherapeutic agents and radiation treatment. The protection can result from both direct action of the amino acid and/or after its conversion to glutathione (GSH), sulfate, or other sulfur-based protective substances. Unfortunately, high GSH levels have been implicated in the problematic development of tumor cells' resistance to therapy. Due to numerous differences in the metabolic processing of the cysteine stereoisomers, chemo- and radioprotective strategies might be developed using the D-form of the amino acid, which can participate in protection directly, but which cannot be used to support GSH biosynthesis. In this way, protection of normal tissue may be achieved, while the potential development of resistance in tumor cells is minimized. Greatly enhanced therapeutic efficacy of cancer treatment regimens may be the result.
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Affiliation(s)
- J C Roberts
- Department of Medicinal Chemistry, University of Utah, 308 Skaggs Hall, 84112, Salt Lake City, UT, USA
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Passera E, Campanini B, Rossi F, Casazza V, Rizzi M, Pellicciari R, Mozzarelli A. Human kynurenine aminotransferase II - reactivity with substrates and inhibitors. FEBS J 2011; 278:1882-900. [DOI: 10.1111/j.1742-4658.2011.08106.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Convergent evolution of coenzyme M biosynthesis in the Methanosarcinales: cysteate synthase evolved from an ancestral threonine synthase. Biochem J 2009; 424:467-78. [PMID: 19761441 DOI: 10.1042/bj20090999] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The euryarchaeon Methanosarcina acetivorans has no homologues of the first three enzymes that produce the essential methanogenic coenzyme M (2-mercaptoethanesulfonate) in Methanocaldococcus jannaschii. A single M. acetivorans gene was heterologously expressed to produce a functional sulfopyruvate decarboxylase protein, the fourth canonical enzyme in this biosynthetic pathway. An adjacent gene, at locus MA3297, encodes one of the organism's two threonine synthase homologues. When both paralogues from this organism were expressed in an Escherichia coli threonine synthase mutant, the MA1610 gene complemented the thrC mutation, whereas the MA3297 gene did not. Both PLP (pyridoxal 5'-phosphate)-dependent proteins were heterologously expressed and purified, but only the MA1610 protein catalysed the canonical threonine synthase reaction. The MA3297 protein specifically catalysed a new beta-replacement reaction that converted L-phosphoserine and sulfite into L-cysteate and inorganic phosphate. This oxygen-independent mode of sulfonate biosynthesis exploits the facile nucleophilic addition of sulfite to an alpha,beta-unsaturated intermediate (PLP-bound dehydroalanine). An amino acid sequence comparison indicates that cysteate synthase evolved from an ancestral threonine synthase through gene duplication, and the remodelling of active site loop regions by amino acid insertion and substitutions. The cysteate product can be converted into sulfopyruvate by an aspartate aminotransferase enzyme, establishing a new convergent pathway for coenzyme M biosynthesis that appears to function in members of the orders Methanosarcinales and Methanomicrobiales. These differences in coenzyme M biosynthesis afford the opportunity to develop methanogen inhibitors that discriminate between the classes of methanogenic archaea.
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13
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Woo CWH, Siow YL, O K. Homocysteine induces monocyte chemoattractant protein-1 expression in hepatocytes mediated via activator protein-1 activation. J Biol Chem 2007; 283:1282-1292. [PMID: 18024959 DOI: 10.1074/jbc.m707886200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hyperhomocysteinemia is characterized by abnormally high concentrations of homocysteine (Hcy) in the plasma. It is a metabolic disorder associated with dysfunction of several organs such as atherosclerosis, altered lipid metabolism, and liver injury. In this study we investigated the effect of Hcy on transcriptional regulation of monocyte chemoattractant protein-1 (MCP-1), a potent chemokine, expression in hepatocytes. Hyperhomocysteinemia was induced in rats by a high-methionine diet for 4 weeks. MCP-1 mRNA and protein levels were significantly elevated in the liver tissue homogenate and in hepatocytes of hyperhomocysteinemic rats. The role of transcription factors in MCP-1 expression was examined by electrophoretic mobility shift assay. Activation of activator protein (AP)-1 but not nuclear factor kappaB was detected in the liver tissue of those rats. Incubation of rat hepatocytes with Hcy (50-200 microm) caused a significant increase in AP-1 activation followed by an increase in intracellular MCP-1 mRNA expression and an elevation of MCP-1 protein secreted into the culture medium. Hcy markedly increased the DNA binding activity of human recombinant AP-1 (c-Fos and c-Jun proteins). The presence of a sulfhydryl group in Hcy was essential for Hcy-induced AP-1 activation. When hepatocytes were transfected with decoy AP-1 oligodeoxynucleotide to inhibit AP-1 activation, Hcy-induced MCP-1 mRNA expression was abolished. Further analysis revealed that increased hepatic MCP-1 expression was positively correlated with the serum MCP-1 level. These results suggest that Hcy-induced MCP-1 expression in the liver is mediated via AP-1 activation, which may contribute to chronic inflammation associated with hyperhomocysteinemia.
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Affiliation(s)
- Connie W H Woo
- Departments of Animal Science and Physiology, University of Manitoba, Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg R2H 2A6, Canada
| | - Yaw L Siow
- Departments of Animal Science and Physiology, University of Manitoba, Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg R2H 2A6, Canada
| | - Karmin O
- Departments of Animal Science and Physiology, University of Manitoba, Canadian Centre for Agri-Food Research in Health and Medicine, St. Boniface Hospital Research Centre, Winnipeg R2H 2A6, Canada.
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15
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Abstract
The first major step of cysteine catabolism, the oxidation of cysteine to cysteine sulfinic acid, is catalyzed by cysteine dioxygenase (CDO). In the present work, we utilize recombinant rat liver CDO and cysteine derivatives to elucidate structural parameters involved in substrate recognition and x-ray absorption spectroscopy to probe the interaction of the active site iron center with cysteine. Kinetic studies using cysteine structural analogs show that most are inhibitors and that a terminal functional group bearing a negative charge (e.g. a carboxylate) is required for binding. The substrate-binding site has no stringent restrictions with respect to the size of the amino acid. Lack of the amino or carboxyl groups at the alpha-carbon does not prevent the molecules from interacting with the active site. In fact, cysteamine is shown to be a potent activator of the enzyme without being a substrate. CDO was also rendered inactive upon complexation with the metal-binding inhibitors azide and cyanide. Unlike many non-heme iron dioxygenases that employ alpha-keto acids as cofactors, CDO was shown to be the only dioxygenase known to be inhibited by alpha-ketoglutarate.
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Affiliation(s)
- Sergio C Chai
- Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Chai SC, Jerkins AA, Banik JJ, Shalev I, Pinkham JL, Uden PC, Maroney MJ. Heterologous expression, purification, and characterization of recombinant rat cysteine dioxygenase. J Biol Chem 2004; 280:9865-9. [PMID: 15623508 DOI: 10.1074/jbc.m413733200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cysteine dioxygenase (CDO, EC 1.13.11.20) catalyzes the oxidation of cysteine to cysteine sulfinic acid, which is the first major step in cysteine catabolism in mammalian tissues. Rat liver CDO was cloned and expressed in Escherichia coli as a 26.8-kDa N-terminal fusion protein bearing a polyhistidine tag. Purification by immobilized metal affinity chromatography yielded homogeneous protein, which was catalytically active even in the absence of the secondary protein-A, which has been reported to be essential for activity in partially purified native preparations. As compared with those existing purification protocols for native CDO, the milder conditions used in the isolation of the recombinant CDO allowed a more controlled study of the properties and activity of CDO, clarifying conflicting findings in the literature. Apo-protein was inactive in catalysis and was only activated by iron. Metal analysis of purified recombinant protein indicated that only 10% of the protein contained iron and that the iron was loosely bound to the protein. Kinetic studies showed that the recombinant enzyme displayed a K(m) value of 2.5 +/- 0.4 mm at pH 7.5 and 37 degrees C. The enzyme was shown to be specific for l-cysteine oxidation, whereas homocysteine inhibited CDO activity.
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Affiliation(s)
- Sergio C Chai
- Department of Chemistry and Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA
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Abstract
In order to evaluate the effect of hypotaurine on ethanol-induced locomotion, different groups of mice received an injection of saline or 5.62, 8.45, 11.25, 16.87 or 33.75 mg/kg of hypotaurine 30 min prior to administering ethanol (2.4 g/kg). The duration of the effect of hypotaurine was explored by treating animals with ethanol 0, 30, 60 and 90 min after hypotaurine pretreatment. The effect of hypotaurine on acute stimulating ethanol locomotion was evaluated by pretreating animals with saline or 11.25 mg/kg of hypotaurine 30 or 60 min before ethanol (1.6, 2.4, 3.2 g/kg) or saline injections. Hypotaurine (11.25 mg/kg) required 30 min to boost, specifically ethanol-stimulated locomotion (2.4 g/kg). These results suggest a central locus for the interaction, firstly, because blood ethanol levels were not different between hypotaurine and saline pretreated mice, and, secondly, because a cotreatment with beta-alanine (22 mg/kg), a beta-amino acid that counteracts the transfer of hypotaurine across the blood-brain barrier (BBB), prevented the enhancement in ethanol-induced locomotion produced by hypotaurine.
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Affiliation(s)
- L Font
- Area de Psicobiologia, Universitat Jaume I, Aptdo 221, 8029AP Castelló, 12080, Spain
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Metzler DE, Metzler CM, Sauke DJ. The Metabolism of Nitrogen and Amino Acids. Biochemistry 2001. [DOI: 10.1016/b978-012492543-4/50027-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Graber R, Kasper P, Malashkevich VN, Strop P, Gehring H, Jansonius JN, Christen P. Conversion of aspartate aminotransferase into an L-aspartate beta-decarboxylase by a triple active-site mutation. J Biol Chem 1999; 274:31203-8. [PMID: 10531314 DOI: 10.1074/jbc.274.44.31203] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The conjoint substitution of three active-site residues in aspartate aminotransferase (AspAT) of Escherichia coli (Y225R/R292K/R386A) increases the ratio of L-aspartate beta-decarboxylase activity to transaminase activity >25 million-fold. This result was achieved by combining an arginine shift mutation (Y225R/R386A) with a conservative substitution of a substrate-binding residue (R292K). In the wild-type enzyme, Arg(386) interacts with the alpha-carboxylate group of the substrate and is one of the four residues that are invariant in all aminotransferases; Tyr(225) is in its vicinity, forming a hydrogen bond with O-3' of the cofactor; and Arg(292) interacts with the distal carboxylate group of the substrate. In the triple-mutant enzyme, k(cat)' for beta-decarboxylation of L-aspartate was 0.08 s(-1), whereas k(cat)' for transamination was decreased to 0.01 s(-1). AspAT was thus converted into an L-aspartate beta-decarboxylase that catalyzes transamination as a side reaction. The major pathway of beta-decarboxylation directly produces L-alanine without intermediary formation of pyruvate. The various single- or double-mutant AspATs corresponding to the triple-mutant enzyme showed, with the exception of AspAT Y225R/R386A, no measurable or only very low beta-decarboxylase activity. The arginine shift mutation Y225R/R386A elicits beta-decarboxylase activity, whereas the R292K substitution suppresses transaminase activity. The reaction specificity of the triple-mutant enzyme is thus achieved in the same way as that of wild-type pyridoxal 5'-phosphate-dependent enzymes in general and possibly of many other enzymes, i.e. by accelerating the specific reaction and suppressing potential side reactions.
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Affiliation(s)
- R Graber
- Biochemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland
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Edgar SE, Kirk CA, Rogers QR, Morris JG. Taurine status in cats is not maintained by dietary cysteinesulfinic acid. J Nutr 1998; 128:751-7. [PMID: 9521639 DOI: 10.1093/jn/128.4.751] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Endogenous synthesis of taurine by cats is limited. Putative precursors of taurine, cysteinesulfinic acid and cysteic acid, were fed to cats to determine whether they were utilized. Groups of five cats were depleted of taurine by a resin (Colestipol(R)) diet, then given 6 dietary treatments containing (g/kg diet): 0.0, 0.4, or 0.8 taurine; or 0.98 or 1.96 cysteinesulfinic acid, or 0.4 taurine + 1.0 cysteic acid for 12 wk. Plasma and whole blood taurine concentrations and body weights were measured weekly. Concentration of taurine in semitendinosus muscle was measured initially, after 2 wk of taurine depletion (after resin-diet), and monthly thereafter. The resin diet decreased concentrations of taurine in plasma, whole blood, and muscle to 0.20, 0.49, and 0.37 of initial values, respectively. Cysteinesulfinic acid diets resulted in no significant (P > 0.05) increase in the concentration of taurine in plasma, whole blood, or muscle, and no increased excretion of cysteinesulfinate or taurine in urine or feces. Cats fed the diets containing 1.0 g cysteic acid + 0.4 g taurine, or 0.8 g taurine/kg diet had similar concentrations of taurine in plasma, whole blood, and muscle. Aminotransferase activity for cysteinesulfinic acid in the liver and intestinal mucosa of cats and rats was higher than that for aspartic or cysteic acids. Transamination of dietary cysteinesulfinic acid to beta-sulfinylpyruvate (which spontaneously decomposes), rather than decarboxylation is postulated as the basis for no detectable conversion to taurine. In contrast, cysteic acid is reversibly transaminated to beta-sulfopyruvate which is stable and thereby is a precursor for taurine in cats.
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Affiliation(s)
- S E Edgar
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616-8741, USA
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21
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Malmezat T, Breuillé D, Pouyet C, Mirand PP, Obled C. Metabolism of cysteine is modified during the acute phase of sepsis in rats. J Nutr 1998; 128:97-105. [PMID: 9430609 DOI: 10.1093/jn/128.1.97] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In vivo cysteine metabolism during the inflammatory state has been studied minimally. We investigated cysteine metabolism (i.e. taurine, sulfate and glutathione formation) using a single dose of [35S] cysteine in septic rats that had been injected with live Escherichia coli into the tail vein and in control, pair-fed rats. Cysteine metabolites were separated by ion exchange chromatography, and radioactivity was counted in the different fractions. Radioactivity incorporated in tissue proteins was also measured after protein precipitation. [35S]Sulfate production was significantly lower in septic rats than in pair-fed rats. [35S]Taurine contents were significantly lower only in kidneys, spleen and gastrointestinal tract of septic rats. The higher production of [35S] taurine in the livers (the major site of taurine production) of septic rats could have a protective effect against oxidation. Glutathione concentrations were also significantly greater in liver, spleen, kidneys and gastrocnemius muscle of septic rats, presumably in order to combat oxidative stress induced by sepsis. [35S]Cysteine incorporation in glutathione was significantly higher in spleen and kidneys but not in liver of septic rats compared to pair-fed rats. This could be explained by the fact that, in liver, a greater amount of labeled glutathione had been utilized for host defense, or by a high level in glutathione turnover. Finally, [35S]cysteine incorporation into protein, in septic rats, was significantly greater than in pair-fed rats in spleen, lung and particulary in whole plasma proteins other than albumin, which mainly represent the acute-phase proteins. These data suggest an increased requirement for cysteine during sepsis in rats.
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Affiliation(s)
- T Malmezat
- Laboratoire d'Etude du Métabolisme Azoté, INRA Clermont-Ferrand Theix, 63122 Saint Genès Champanelle, France
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Waterfield CJ, Timbrell JA. The biosynthesis of taurine fromN-acetyl-l-cysteine and other precursorsin vivo and in rat hepatocytes. Amino Acids 1996; 10:173-85. [DOI: 10.1007/bf00806590] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/1995] [Accepted: 10/10/1995] [Indexed: 11/28/2022]
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Bawden CS, Sivaprasad AV, Verma PJ, Walker SK, Rogers GE. Expression of bacterial cysteine biosynthesis genes in transgenic mice and sheep: toward a new in vivo amino acid biosynthesis pathway and improved wool growth. Transgenic Res 1995; 4:87-104. [PMID: 7704055 DOI: 10.1007/bf01969411] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
It is possible to improve wool growth through increasing the supply of cysteine available for protein synthesis and cell division in the wool follicle. As mammals can only synthesise cysteine indirectly from methionine via trans-sulphuration, expression of transgenes encoding microbial cysteine biosynthesis enzymes could provide a more efficient pathway to cysteine synthesis in the sheep. If expressed in the rumen epithelium, the abundant sulphide, produced by ruminal microorganisms and normally excreted, could be captured for conversion to cysteine. This paper describes the characterisation of expression of the cysteine biosynthesis genes of Salmonella typhimurium, cysE, cysM and cysK, and linked cysEM, cysME and cysKE genes as transgenes in mice and sheep. The linked transgenes were constructed with each gene driven by a separate promoter, either with the Rous sarcoma virus long terminal repeat (RSVLTR) promoter or the mouse phosphoglycerate kinase-1 (mPgk-1) promoter, and with human growth hormone (hGH) polyadenylation sequences. Transgenesis of mice with the RSVLTR-cysE gene afforded tissue-specific, heritable expression of the gene. Despite high levels of expression in a number of tissues, extremely low levels of expression occurred in the stomach and small intestine. Results of a concurrent sheep transgenesis experiment using the RSVLTR-cysEM and -cysME linked transgenes revealed that the RSVLTR promoter was inadequate for expression in the rumen. Moreover, instability of transgenes containing the RSVLTR sequence was observed. Expression of mPgk-cysME and -cysKE linked transgenes in most tissues of the mice examined, including the stomach and small intestine, suggested this promoter to be a better candidate for expression of these transgenes in the analogous tissues of sheep. However, a subsequent sheep transgenesis experiment indicated that use of the mPgk-1 promoter, active ubiquitously and early in development, may be inappropriate for expression of the cysteine biosynthesis transgenes. In summary, these results indicate that enzymically active bacterial cysteine biosynthesis gene products can be coexpressed in mammalian cells in vivo but that expression of the genes should be spatio-temporally restricted to the adult sheep rumen epithelium.
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Affiliation(s)
- C S Bawden
- Department of Biochemistry, University of Adelaide, South Australia
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Plasma cysteine concentrations in infants with respiratory distress. The journal The Journal of Pediatrics 1994. [DOI: 10.1016/s0022-3476(06)80182-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Ide T, Horii M, Yamamoto T, Kawashima K. Contrasting effects of water-soluble and water-insoluble dietary fibers on bile acid conjugation and taurine metabolism in the rat. Lipids 1990; 25:335-40. [PMID: 2164126 DOI: 10.1007/bf02544343] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The effect of the type of dietary fiber on the bile acid and taurine metabolism was examined in rats. Diets containing 10% of various water-soluble fibers (citrus pectin, konjak mannan, guar gum) as compared to a fiber-free diet increased biliary excretion of total bile acids. In contrast, water-insoluble dietary fibers (cellulose, corn bran, chitin; 10% in the diets) as well as cholestyramine (5% in the diet) considerably decreased bile acid excretion. Water-soluble dietary fiber-mediated increases in bile acid excretion were totally attributable to increases in glycine-conjugates. Thus, these fibers greatly increased the bile acid glycine-to-taurine ratio (G/T). Excretion of glycine conjugates decreased more than that of taurine conjugates in rats fed various water-insoluble dietary fibers. As a result, G/T in rats fed water-insoluble fibers was significantly lowered as compared to G/T in animals fed a fiber-free diet. Cholestyramine did not affect the G/T ratio of bile acids. Fecal bile acid excretion and the activities of hepatic cholesterol 7 alpha-hydroxylase (EC 1.14.13.17) in rats fed various water-soluble dietary fibers approximately doubled as compared to the respective values for rats fed a fiber-free diet. Whereas cholestyramine greatly increased these parameters, water-insoluble fibers did not significantly affect them. Various water-soluble fibers decreased hepatic concentration and urinary excretion of taurine as well as the activity of hepatic cysteine dioxygenase (EC 1.13.11.20). In contrast, water-insoluble fibers considerably increased hepatic taurine concentrations and enzyme activities. The parameters for taurine metabolism were unaffected by cholestyramine. It was suggested that the types of dietary fiber affected hepatic taurine synthesis and thus modified bile acid glycine/taurine ratios.
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Affiliation(s)
- T Ide
- National Food Research Institute, Ministry of Agriculture, Forestry and Fisheries, Tsukuba, Japan
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Ide T, Horii M, Kawashima K, Yamamoto T. Bile acid conjugation and hepatic taurine concentration in rats fed on pectin. Br J Nutr 1989; 62:539-50. [PMID: 2605154 DOI: 10.1079/bjn19890056] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A relationship between bile acid conjugation and hepatic taurine concentration was investigated in rats fed on citrus pectin. When rats were fed on the diets containing varying amounts of pectin (10, 30, 60 and 100 g/kg dietary levels), biliary excretion of bile acids increased as the dietary levels of pectin increased. The increase was entirely due to the glycine-conjugated bile acids. The biliary excretion of taurine-conjugated bile acid was somewhat decreased as the dietary level of the fibre increased. Consequently, most of the bile acids were conjugated with glycine in rats fed on the diet containing 100 g pectin/kg. On the other hand, dietary cellulose (60 and 100 g/kg) did not affect the biliary bile acid excretions. The major proportion of bile acids in rats receiving a fibre-free diet and the diets containing cellulose were conjugated with taurine. Hepatic taurine concentrations decreased as the dietary levels of pectin, but not of cellulose, increased. Although dietary pectin (100 g/kg) also slightly decreased the taurine concentration in the kidney, those concentrations in other non-hepatic tissues examined (heart, brain and serum) were unaffected by the dietary fibre. Supplementation of the diet containing 100 g pectin/kg with methionine (10 g/kg) and taurine (10 and 50 g/kg) strikingly increased hepatic taurine concentrations. In this situation, the conjugation of bile acid with glycine was almost abolished and taurine conjugates became abundant in the bile of these animals. It is suggested that dietary pectin mediated an increase in the biliary bile acid excretion which may have depleted the hepatic pool of taurine available for bile acid conjugation and, thus, increased glycine conjugation of bile acids.
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Affiliation(s)
- T Ide
- Laboratory of Nutrition Chemistry, National Food Research Institute, Tsukuba, Japan
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