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MT3/QR2 melatonin binding site does not use melatonin as a substrate or a co‐substrate
Author(s) -
Boutin Jean A.,
Marcheteau Estelle,
Hennig Philippe,
Moulharat Natacha,
Berger Sylvie,
Delagrange Philippe,
Bouchet JeanPaul,
Ferry Gilles
Publication year - 2008
Publication title -
journal of pineal research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.881
H-Index - 131
eISSN - 1600-079X
pISSN - 0742-3098
DOI - 10.1111/j.1600-079x.2008.00631.x
Subject(s) - melatonin , substrate (aquarium) , enzyme , chemistry , redox , reductase , biochemistry , biology , ecology , endocrinology , organic chemistry
Quinone reductase 2 (QR2, E.C. 1.10.99.2) is implicated in cell reactive oxygen species production. The catalytic activity of this enzyme is inhibited by 1 μ m of melatonin. QR2 was identified as the third melatonin binding site (MT3). It is of major importance to understand the exact roles of melatonin and QR2 in oxidative stress. A fascinating possibility that melatonin could serve as a co‐substrate or substrate of QR2 was hypothesized recently. In the current investigation, nuclear magnetic resonance studies of the QR2 catalytic reaction were performed, the results led us to conclude that, whatever the conditions, melatonin is not cleaved off to form N1‐acetyl‐N2‐formyl‐5‐methoxykynurenine by a catalytically active QR2, very strongly indicating that melatonin is neither a substrate nor a co‐substrate of this enzyme. Further studies are needed in order to better understand the relationship between MT3/QR2, melatonin and redox status of the cells, in order to better explain the anti‐oxidant activities of melatonin at pharmacological concentrations (>1 μ m ).