Rs. Koduri et M. Tien, OXIDATION OF GUAIACOL BY LIGNIN PEROXIDASE - ROLE OF VERATRYL ALCOHOL, The Journal of biological chemistry, 270(38), 1995, pp. 22254-22258
We have investigated the Lignin peroxidase-catalyzed oxidation of guai
acol and the role of veratryl alcohol in this reaction by steady-state
and pre-steady-state methods. Pre-steady-state kinetic analyses demon
strated that guaiacol is a good substrate for both compounds I and II,
the two- and one-electron oxidized enzyme intermediates, respectively
, of Lignin peroxidase. The rate constant for the reaction with compou
nd I is 1.2 x 10(6) M(-1) s(-1). The reaction of guaiacol with compoun
d II exhibits a K-d of 64 mu M and a first-order rate constant of 17 s
(-1). Oxridation of guaiacol leads to tetraguaiacol formation. This re
action exhibits classical Michaelis-Menten kinetics with a K-m of 160
mu M and a k(cat) of 7.7 s(-1). Veratryl alcohol, a secondary metaboli
te of ligninolytic fungi, is capable of mediating the oxidation of gua
iacol. This was shown by steady-state inhibition studies. Guaiacol com
pletely inhibited the oxidation of veratryl alcohol, whereas veratryl
alcohol had no corresponding inhibitory effect on guaiacol oxidation,
In fact, at low guaiacol concentrations, veratryl alcohol stimulated t
he rate of guaiacol oxidation. These results collectively demonstrate
that veratryl alcohol can serve as a mediator for phenolic substrates
in the lignin peroxidase reaction.