Redox chemistry in laccase-catalyzed oxidation of N-hydroxy compounds.
1-Hydroxybenzotriazole, violuric acid, and N-hydroxyacetanilide are three N-OH compounds capable of mediating a range of laccase-catalyzed biotransformations, such as paper pulp delignification and degradation of polycyclic hydrocarbons. The mechanism of their enzymatic oxidation was studied with seven fungal laccases. The oxidation had a bell-shaped pH-activity profile with an optimal pH ranging from 4 to 7. The oxidation rate was found to be dependent on the redox potential difference between the N-OH substrate and laccase. A laccase with a higher redox potential or an N-OH compound with a lower redox potential tended to have a higher oxidation rate. Similar to the enzymatic oxidation of phenols, phenoxazines, phenothiazines, and other redox-active compounds, an "outer-sphere" type of single-electron transfer from the substrate to laccase and proton release are speculated to be involved in the rate-limiting step for N-OH oxidation.
Xu
F
F
Novo Nordisk Biotech, Davis, California 95616, USA. fengxu@nnbt.com
Kulys
J J
JJ
Duke
K
K
Li
K
K
Krikstopaitis
K
K
Deussen
H J
HJ
Abbate
E
E
Galinyte
V
V
Schneider
P
P
D000082:Acetaminophen / Q000378:metabolism*; D001463:Barbiturates / Q000378:metabolism*; D001711:Biotransformation; D020171:Botrytis / Q000201:enzymology; D003302:Coprinus / Q000201:enzymology; D005658:Fungi / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D042845:Laccase; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D013379:Substrate Specificity; D014230:Triazoles / Q000378:metabolism*
D001463:Barbiturates; D014230:Triazoles; C094277:violuric acid; D000082:Acetaminophen; C011852:1-hydroxybenzotriazole; D010088:Oxidoreductases; D042845:Laccase