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A quinonoid is an intermediate of oxidative deamination reaction catalyzed by Dopa decarboxylase
Author(s) -
Bertoldi Mariarita,
Cellini Barbara,
Maras Bruno,
Voltattorni Carla Borri
Publication year - 2005
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2005.08.029
Subject(s) - oxidative deamination , deamination , enantiomer , chemistry , substrate (aquarium) , active site , oxidative phosphorylation , catalysis , stereochemistry , enzyme , tryptophan , reaction rate constant , kinetics , medicinal chemistry , biochemistry , amino acid , biology , ecology , physics , quantum mechanics
The reactions of Dopa decarboxylase (DDC) with l ‐ and d ‐enantiomers of tryptophan methyl ester are described. Although both the enantiomers bind to the active site of the enzyme with similar affinity, their binding modes are different. l ‐enantiomer binds in an unproductive mode, while d ‐enantiomer acts as an oxidative deamination substrate. For the first time a quinonoid has been detected as intermediate of this reaction. By using rapid‐scanning stopped‐flow kinetic technique rate constants for formation and decay of this species have been determined. All these data, besides validating the functional DDC active site model, represent an important step toward the elucidation of the catalytic pathway of oxidative deamination.