The MttB superfamily member MtyB from the human gut symbiont Eubacterium limosum is a cobalamin-dependent γ-butyrobetaine methyltransferase.

Autor: Ellenbogen JB; Department of Microbiology, The Ohio State University, Columbus, Ohio, USA., Jiang R; Department of Microbiology, The Ohio State University, Columbus, Ohio, USA., Kountz DJ; Department of Microbiology, The Ohio State University, Columbus, Ohio, USA., Zhang L; Campus Chemical Instrument Center Mass Spectrometry and Proteomics Facility, The Ohio State University, Columbus, Ohio, USA., Krzycki JA; Department of Microbiology, The Ohio State University, Columbus, Ohio, USA; The Ohio State Biochemistry Program, The Ohio State University, Columbus, Ohio, USA. Electronic address: Krzycki.1@osu.edu.
Jazyk: angličtina
Zdroj: The Journal of biological chemistry [J Biol Chem] 2021 Nov; Vol. 297 (5), pp. 101327. Date of Electronic Publication: 2021 Oct 21.
DOI: 10.1016/j.jbc.2021.101327
Abstrakt: The production of trimethylamine (TMA) from quaternary amines such as l-carnitine or γ-butyrobetaine (4-(trimethylammonio)butanoate) by gut microbial enzymes has been linked to heart disease. This has led to interest in enzymes of the gut microbiome that might ameliorate net TMA production, such as members of the MttB superfamily of proteins, which can demethylate TMA (e.g., MttB) or l-carnitine (e.g., MtcB). Here, we show that the human gut acetogen Eubacterium limosum demethylates γ-butyrobetaine and produces MtyB, a previously uncharacterized MttB superfamily member catalyzing the demethylation of γ-butyrobetaine. Proteomic analyses of E. limosum grown on either γ-butyrobetaine or dl-lactate were employed to identify candidate proteins underlying catabolic demethylation of the growth substrate. Three proteins were significantly elevated in abundance in γ-butyrobetaine-grown cells: MtyB, MtqC (a corrinoid-binding protein), and MtqA (a corrinoid:tetrahydrofolate methyltransferase). Together, these proteins act as a γ-butyrobetaine:tetrahydrofolate methyltransferase system, forming a key intermediate of acetogenesis. Recombinant MtyB acts as a γ-butyrobetaine:MtqC methyltransferase but cannot methylate free cobalamin cofactor. MtyB is very similar to MtcB, the carnitine methyltransferase, but neither was detectable in cells grown on carnitine nor was detectable in cells grown with γ-butyrobetaine. Both quaternary amines are substrates for either enzyme, but kinetic analysis revealed that, in comparison to MtcB, MtyB has a lower apparent K m for γ-butyrobetaine and higher apparent V max , providing a rationale for MtyB abundance in γ-butyrobetaine-grown cells. As TMA is readily produced from γ-butyrobetaine, organisms with MtyB-like proteins may provide a means to lower levels of TMA and proatherogenic TMA-N-oxide via precursor competition.
Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article.
(Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)
Databáze: MEDLINE
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