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Characterization of an intradiol dioxygenase involved in the biodegradation of the chlorophenoxy herbicides 2,4‐D and 2,4,5‐T
Author(s) -
Travkin V.M,
Jadan A.P,
Briganti F,
Scozzafava A,
Golovleva L.A
Publication year - 1997
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/s0014-5793(97)00297-4
Subject(s) - dioxygenase , chemistry , substrate (aquarium) , dimer , enzyme , stereochemistry , electron paramagnetic resonance , absorption spectroscopy , photochemistry , crystallography , organic chemistry , nuclear magnetic resonance , oceanography , physics , quantum mechanics , geology
Hydroxyquinol 1,2‐dioxygenase, an intradiol dioxygenase, which catalyzes the cleaving of the aromatic ring of hydroxyquinol, a key intermediate of 2,4‐D and 2,4,5‐T degradation, was purified from Nocardioides simplex 3E cells grown on 2,4‐D as the sole carbon source. This enzyme exhibits a highly restricted substrate specificity and is able to cleave hydroxyquinol ( K m for hydroxyquinol as a substrate was 1.2 μM, V max 55 U/mg, K cat 57 s −1 and K cat / K m 47.5 μM s −1 ), 6‐chloro‐ and 5‐chlorohydroxyquinol. Different substituted catechols and hydroquinones are not substrates for this enzyme. This enzyme appears to be a dimer with two identical 37‐kDa subunits. Protein and iron analyses indicate an iron stoichiometry of 1 iron/65 kDa homodimer, α 2 Fe. Both the electronic absorption spectrum which shows a broad absorption band with a maximum at 450 nm and the electron paramagnetic resonance spectra are consistent with a high‐spin iron(III) ion in a rhombic environment typical of the active site of intradiol cleaving enzymes.