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The effect of methyl acceptors on betaine metabolism and the fate of betaine‐derived methyl groups in rat hepatocytes
Author(s) -
Treberg Jason Robert,
Silva Robin P.,
Brosnan Margaret E.,
Brosnan John T.
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.613.3
Subject(s) - betaine , chemistry , metabolism , biochemistry , methionine , choline , serine , homocysteine , glycine , methyl group , catabolism , stereochemistry , enzyme , amino acid , organic chemistry , alkyl
Despite well articulated metabolic pathways, little is known of how betaine metabolism is regulated or what controls its catabolism and the fate of the three methyl groups of the trimethylamine moiety. Using rat primary hepatocytes we investigated the metabolism of 3‐[ 14 CH 3 ]‐labeled betaine. This study, for the first time, explores the fate of the betaine methyl groups in isolated liver cells. Approximately 50% of the metabolised methyl groups are found in an acid soluble fraction that, based on ion exchange chromatography, is consistent with the products of betaine:homocysteine methyltransferase, methionine and dimethylglycine. The remaining methyl groups were metabolised to volatile compounds, likely CO 2 or formate. Betaine concentration did not affect the relative proportion of label found in the volatile fraction. Total product formation from betaine has an apparent K m of 0.41 mM, somewhat above arterial plasma values (∼ 0.1–0.2 mM). The addition of homocysteine as a methyl acceptor had no effect on betaine metabolism; however, glycine (methyl acceptor and precursor of serine) markedly decreases the relative amount of volatile product formation. This work was funded by CIHR.