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Interaction of liver methionine adenosyltransferase with hydroxyl radical
Author(s) -
SánchezGóngora E.,
Ruiz F.,
Mingorance J.,
An W.,
Corrales F. J.,
Mato J. M.
Publication year - 1997
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.11.12.9337154
Subject(s) - methionine adenosyltransferase , cysteine , biochemistry , chinese hamster ovary cell , methionine , chemistry , enzyme , serine , cysteine metabolism , mutant , amino acid , receptor , gene
Liver methionine adenosyltransferase (MAT) plays a critical role in the metabolism of methionine converting this amino acid, in the presence of ATP, into S‐adenosylmethionine. Here we report that hydrogen peroxide (H 2 O 2 ), via generation of hydroxyl radical, inactivates liver MAT by reversibly and covalently oxidizing an enzyme site. In vitro studies using pure liver recombinant enzyme and mutants of MAT, where each of the 10 cysteine residues of the enzyme subunit were individually changed to serine by site‐directed mutagenesis, identified cysteine 121 as the site of molecular interaction between H 2 O 2 and liver MAT. Cysteine 121 is specific to the hepatic enzyme and is localized at a “flexible loop” over the active site cleft of MAT. In vivo studies, using wild‐type Chinese hamster ovary (CHO) cells and CHO cells stably expressing liver MAT, demonstrate that the inactivation of MAT by H 2 O 2 is specific to the hepatic enzyme, resulting from the modification of the cysteine residue 121, and that this effect is mediated by the generation of the hydroxyl radical. Our results suggest that H 2 O 2 ‐induced MAT inactivation might be the cause of reduced MAT activity and abnormal methionine metabolism observed in patients with alcoholic liver disease.—Sánchez‐Góngora, E., Ruiz, F., Mingorance, J., An, W., Corrales, F. J., and Mato, J. M. Interaction of liver methionine adenosyltransferase with hydroxyl radical. FASEB J. 11, 1013–1019 (1997)