Publications

• Gamma-butyrobetaine is a proatherogenic intermediate in gut microbial metabolism of L-carnitine to TMAO.

  Koeth R.A., Levison B.S., Culley M.K., Buffa J.A., Wang Z., Gregory J.C., Org E., Wu Y., Li L., Smith J.D., Tang W.H., DiDonato J.A., Lusis A.J., Hazen S.L.

  L-carnitine, a nutrient in red meat, was recently reported to accelerate atherosclerosis via a metaorganismal pathway involving gut microbial trimethylamine (TMA) formation and host hepatic conversion into trimethylamine-N-oxide (TMAO). Herein, we show that following L-carnitine ingestion, γ-butyr ... >> More

  L-carnitine, a nutrient in red meat, was recently reported to accelerate atherosclerosis via a metaorganismal pathway involving gut microbial trimethylamine (TMA) formation and host hepatic conversion into trimethylamine-N-oxide (TMAO). Herein, we show that following L-carnitine ingestion, γ-butyrobetaine (γBB) is produced as an intermediary metabolite by gut microbes at a site anatomically proximal to and at a rate ∼1,000-fold higher than the formation of TMA. Moreover, we show that γBB is the major gut microbial metabolite formed from dietary L-carnitine in mice, is converted into TMA and TMAO in a gut microbiota-dependent manner (like dietary L-carnitine), and accelerates atherosclerosis. Gut microbial composition and functional metabolic studies reveal that distinct taxa are associated with the production of γBB or TMA/TMAO from dietary L-carnitine. Moreover, despite their close structural similarity, chronic dietary exposure to L-carnitine or γBB promotes development of functionally distinct microbial communities optimized for the metabolism of L-carnitine or γBB, respectively. << Less

  Cell Metab. 20:799-812(2014) [PubMed] [EuropePMC]

  This publication is cited by 4 other entries.

• Carnitine metabolism in the human gut: characterization of the two-component carnitine monooxygenase CntAB from <i>Acinetobacter baumannii</i>.

  Massmig M., Reijerse E., Krausze J., Laurich C., Lubitz W., Jahn D., Moser J.

  Bacterial formation of trimethylamine (TMA) from carnitine in the gut microbiome has been linked to cardiovascular disease. During this process, the two-component carnitine monooxygenase (CntAB) catalyzes the oxygen-dependent cleavage of carnitine to TMA and malic semialdehyde. Individual redox st ... >> More

  Bacterial formation of trimethylamine (TMA) from carnitine in the gut microbiome has been linked to cardiovascular disease. During this process, the two-component carnitine monooxygenase (CntAB) catalyzes the oxygen-dependent cleavage of carnitine to TMA and malic semialdehyde. Individual redox states of the reductase CntB and the catalytic component CntA were investigated based on mutagenesis and electron paramagnetic resonance (EPR) spectroscopic approaches. Protein ligands of the flavin mononucleotide (FMN) and the plant-type [2Fe-2S] cluster of CntB and also of the Rieske-type [2Fe-2S] cluster and the mononuclear [Fe] center of CntA were identified. EPR spectroscopy of variant CntA proteins suggested a hierarchical metallocenter maturation, Rieske [2Fe-2S] followed by the mononuclear [Fe] center. NADH-dependent electron transfer <i>via</i> the redox components of CntB and within the trimeric CntA complex for the activation of molecular oxygen was investigated. EPR experiments indicated that the two electrons from NADH were allocated to the plant-type [2Fe-2S] cluster and to FMN in the form of a flavin semiquinone radical. Single-turnover experiments of this reduced CntB species indicated the translocation of the first electron onto the [Fe] center and the second electron onto the Rieske-type [2Fe-2S] cluster of CntA to finally allow for oxygen activation as a basis for carnitine cleavage. EPR spectroscopic investigation of CntA variants indicated an unusual intermolecular electron transfer between the subunits of the CntA trimer <i>via</i> the "bridging" residue Glu-205. On the basis of these data, a redox catalytic cycle for carnitine monooxygenase was proposed. << Less

  J Biol Chem 295:13065-13078(2020) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota.

  Zhu Y., Jameson E., Crosatti M., Schaefer H., Rajakumar K., Bugg T.D., Chen Y.

  Dietary intake of L-carnitine can promote cardiovascular diseases in humans through microbial production of trimethylamine (TMA) and its subsequent oxidation to trimethylamine N-oxide by hepatic flavin-containing monooxygenases. Although our microbiota are responsible for TMA formation from carnit ... >> More

  Dietary intake of L-carnitine can promote cardiovascular diseases in humans through microbial production of trimethylamine (TMA) and its subsequent oxidation to trimethylamine N-oxide by hepatic flavin-containing monooxygenases. Although our microbiota are responsible for TMA formation from carnitine, the underpinning molecular and biochemical mechanisms remain unclear. In this study, using bioinformatics approaches, we first identified a two-component Rieske-type oxygenase/reductase (CntAB) and associated gene cluster proposed to be involved in carnitine metabolism in representative genomes of the human microbiota. CntA belongs to a group of previously uncharacterized Rieske-type proteins and has an unusual "bridging" glutamate but not the aspartate residue, which is believed to facilitate intersubunit electron transfer between the Rieske center and the catalytic mononuclear iron center. Using Acinetobacter baumannii as the model, we then demonstrate that cntAB is essential in carnitine degradation to TMA. Heterologous overexpression of cntAB enables Escherichia coli to produce TMA, confirming that these genes are sufficient in TMA formation. Site-directed mutagenesis experiments have confirmed that this unusual "bridging glutamate" residue in CntA is essential in catalysis and neither mutant (E205D, E205A) is able to produce TMA. Taken together, the data in our study reveal the molecular and biochemical mechanisms underpinning carnitine metabolism to TMA in human microbiota and assign the role of this novel group of Rieske-type proteins in microbial carnitine metabolism. << Less

  Proc. Natl. Acad. Sci. U.S.A. 111:4268-4273(2014) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.

• L-carnitine via enzyme-catalyzed oxidative kinetic resolution.

  Ditullio D., Anderson D., Chen C.S., Sih C.J.

  L-Carnitine of high optical purity was prepared via kinetic resolution using a mutant strain of Acinetobacter calcoaceticus ATCC 39647. This organism preferentially metabolized the D-enantiomer of the racemate to furnish L-carnitine. Recovery of L-carnitine was 93%, providing a total weight yield ... >> More

  L-Carnitine of high optical purity was prepared via kinetic resolution using a mutant strain of Acinetobacter calcoaceticus ATCC 39647. This organism preferentially metabolized the D-enantiomer of the racemate to furnish L-carnitine. Recovery of L-carnitine was 93%, providing a total weight yield of 46.5% in 92% enantiomeric excess. The mode of degradation of carnitine was shown to proceed via a monooxygenase-catalyzed oxidative cleavage resulting in the formation of trimethylamine and malic acid. The data suggest that the stereoselective metabolism of DL-carnitine is probably the result of differential permeability of the cell membrane towards the optical antipodes. << Less

  Bioorg. Med. Chem. 2:415-420(1994) [PubMed] [EuropePMC]

  This publication is cited by 1 other entry.