Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota
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In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 111, No. 11, 18.03.2014, p. 4268-73.
Research output: Contribution to journal › Article › peer-review
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T1 - Carnitine metabolism to trimethylamine by an unusual Rieske-type oxygenase from human microbiota
AU - Zhu, Yijun
AU - Jameson, Eleanor
AU - Crosatti, Marialuisa
AU - Schäfer, Hendrik
AU - Rajakumar, Kumar
AU - Bugg, Timothy D H
AU - Chen, Yin
PY - 2014/3/18
Y1 - 2014/3/18
N2 - 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.
AB - 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.
KW - Acinetobacter baumannii/metabolism
KW - Carnitine/metabolism
KW - Chromatography, Ion Exchange
KW - Computational Biology
KW - Escherichia coli
KW - Humans
KW - Methylamines/metabolism
KW - Microbiota/genetics
KW - Mutagenesis, Site-Directed
KW - Oxidoreductases/metabolism
KW - Oxygenases/metabolism
KW - Spectrophotometry, Ultraviolet
U2 - 10.1073/pnas.1316569111
DO - 10.1073/pnas.1316569111
M3 - Article
C2 - 24591617
VL - 111
SP - 4268
EP - 4273
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
SN - 0027-8424
IS - 11
ER -