ANAEROBIC STOPPED-FLOW STUDIES OF INDOLE-3-ACETIC-ACID OXIDATION BY DIOXYGEN CATALYZED BY HORSERADISH-C AND ANIONIC TOBACCO PEROXIDASE AT NEUTRAL PH - CATALASE EFFECT
Ig. Gazarian et Lm. Lagrimini, ANAEROBIC STOPPED-FLOW STUDIES OF INDOLE-3-ACETIC-ACID OXIDATION BY DIOXYGEN CATALYZED BY HORSERADISH-C AND ANIONIC TOBACCO PEROXIDASE AT NEUTRAL PH - CATALASE EFFECT, Biophysical chemistry, 72(3), 1998, pp. 231-237
The effect of order of reagent mixing in the absence and in the presen
ce of catalase on the transient kinetics of indole-3-acetic acid (IAA)
oxidation by dioxygen catalysed by horseradish peroxidase C and anion
ic tobacco peroxidase at neutral pH has been studied. The data suggest
that haem-containing plant peroxidases are able to catalyse the react
ion in the absence of exogenous hydroperoxide. The initiation proceeds
via the formation of the ternary complex enzyme --> IAA --> oxygen re
sponsible for IAA primary radical generation. The horseradish peroxida
se-catalysed reaction is independent of catalase indicating a signific
ant contribution of free radical processes into the overall mechanism.
This is in contrast to the tobacco peroxidase-catalysed reaction wher
e the peroxidase cycle plays an important role. The transient kinetics
of IAA oxidation catalysed by tobacco peroxidase exhibits a biphasic
character with the first phase affected by catalase. The first phase i
s therefore associated with the common peroxidase cycle while the seco
nd is ascribed to native enzyme interaction with skatole peroxy radica
ls yielding directly Compound II. (C) 1998 Elsevier Science B.V. All r
ights reserved.