Transient and Steady-State Kinetics of the Oxidation of Scopoletin by Horseradish Peroxidase Compounds I, II and III in the Presence of NADH

We investigated the possible inhibitory effect of NADH on the reaction of scopoletin with horseradish peroxidase and the effect of scopoletin on the NADH reaction

Leah A. Marquez; H. Brian Dunford

2004

Scholarcy highlights

  • Scopoletin, a naturally occurring fluorescent component of some plants and a proven plant growth inhibitor, is a known reactant with peroxidase
  • The kinetics of the elementary steps of the reaction have never been investigated, nor has the quantitative effect of interfering substances ever been explored in detail, despite the fact that scopoletin is widely used in a peroxidase assay for H2O2
  • We investigated the possible inhibitory effect of NADH on the reaction of scopoletin with horseradish peroxidase and the effect of scopoletin on the NADH reaction
  • Scopoletin stimulates the oxidation of NADH by the HRP/H2O2 system, apparently by forming a phenoxyl radical which oxidizes NADH to NAD· radicals
  • Addition of scopoletin to the HRP/NADH system leads to a biphasic reaction in which HRP-II and HRP-III disappear
  • Our present work provides rate constants for the oxidation of scopoletin by horseradish peroxidase-I, II and III and elucidates the interactions that possibly occur physiologically during NADH oxidation in the presence of scopoletin

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