The Oxidation of Indole Derivatives Catalyzed by Horseradish Peroxidase Is Highly Chemiluminescent* 1 (original) (raw)
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The Oxidation of Indole Derivatives Catalyzed by Horseradish Peroxidase Is Highly Chemiluminescent
Archives of Biochemistry and Biophysics, 2001
The indole moeity is present in many substances of biological occurrence. Its metabolism, in most cases, involves an oxidative pathway. This study reports the oxidation of a series of indole derivatives, including several of biological origin, catalyzed by horseradish peroxidase in the presence of H 2 O 2. Chemiluminescence emission was observed in most cases and its intensity and spectral characteristics were correlated with structural features of the substrates. The structures of the main products were determined. The participation of molecular oxygen and superoxide ion in the reaction was demonstrated and a general mechanism for product formation proposed. Since the oxidation of 2-methylindole proved to be highly chemiluminescent, its potentiality as a developing system for peroxidase-based assays was tested and showed to be very effective.
FEBS Letters, 1993
The effect of xanthene dyes on the chemiluminescence from the aerobic indole‐3‐acetic acid (IAA) oxidation, catalyzed by horseradish peroxidase (HRP), was studied. The rate of IAA oxidation and dye destruction were controlled. It was found that the addition of dyes to the IAA/HRP/O2 system resulted in: (i) the appearance of emission in the region of dye fluorescence, (ii) an increase of the total chemiluminescence intensity, (iii) a decrease of the emission duration, (iv) the acceleration of IAA oxidation, and (v) slow bleaching of the dyes. The experimental results lead to the conclusion that all spectral and kinetic variations of the chemiluminescence from the IAA/HRP/O2 system which are caused by the addition of xanthene dyes, are the result of IAA‐dye co‐oxidation. Earlier published reports regarding energy transfer from electronically excited species, generated in the IAA/HRP/O2 system, to the xanthene dyes seem to be erroneous.
Archives of Biochemistry and Biophysics, 2002
A comparative study on the reactivity of five indole derivatives (tryptamine, N-acetyltryptamine, tryptophan, melatonin, and serotonin), with the redox intermediates compound I (k 2 ) and compound II (k 3 ) of the plant enzyme horseradish peroxidase (HRP) and the two mammalian enzymes lactoperoxidase (LPO) and myeloperoxidase (MPO), was performed using the sequentialmixing stopped-flow technique. The calculated bimolecular rate constants (k 2 , k 3 ) revealed substantial differences regarding the oxidizability of the substrates by redox intermediates at pH 7.0 and 25°C. With HRP it was shown that k 2 and k 3 are mainly determined by the reduction potential (E°) of the substrate with k 2 being 7-45 times higher than k 3 . Compound I of mammalian peroxidases was a much better oxidant than HRP compound I with the consequence that the influence of the indole structure on k 2 of LPO and MPO was small varying by a factor of only 88 and 38, respectively, which is in strong contrast to a factor of 160,000 determined for k 2 of HRP. Interestingly, the k 3 values for all three enzymes were very similar. Oxidation of substrates by mammalian peroxidase compound II is stronly constrained by the nature of the substrate. The k 3 values for the five indoles varied by a factor of 3,570 (LPO) and 200,000 (MPO), suggesting that the reduction potential of compound II of mammalian peroxidase is less positive than that of compound I, which is in contrast to the plant enzyme. © 2002 Elsevier Science
Inhibition of enzymatic indole-3-acetic acid oxidation by phenols
Phytochemistry, 1994
The influence of natural and unnatural phenolic inhibitors on peroxidase-catalyzed oxidation of indole-3-acetic acid (IAA) was investigated using chemiluminescent and spectrophotometric methods. The threshold effect under inhibition was observed for all studied phenolic compounds. The IAA oxidation stopped only if the concentration of inhibitor was more than some threshold value. The spontaneous reinitiation of the stopped reaction was also investigated. The system of chemical reactions, required for the description of threshold effect under inhibition and spontaneous reinitiation of stopped reaction, was proposed. Moreover, the effect of Hz02 on the inhibited IAA oxidation was studied. It was found that addition of HzOz caused a reinitiation of stopped reaction. Threshold effect was observed for the reinitiation. The reinitiation took place only when the concentration of Hz02 was more than a threshold value which depended on the inhibitor concentration. The total quantity of Hz02 required for the reaction reinitiation on the addition of H,02 a little at a time was more than that on addition by a single large portion. The results obtained are discussed in terms of free-radical chain reaction of enzymatic IAA oxidation.
Oxidation chemistry and biochemistry of indole and effect of its oxidation product in albino mice
Bioelectrochemistry and Bioenergetics, 1998
Electrochemical oxidation of Indole has been studied in phosphate buffers in the pH range 2.0-10.6 at pyrolytic graphite electrode. Below pH 6.0, the oxidation of Indole occurred in a single 1e step. The nature of the electrode reaction was found as EC in which charge transfer is followed by irreversible chemical step. A UV absorbing intermediate was noticed at around 235 nm which decayed in a pseudo first order reaction to give trimer as the major product. The trimer was characterized by m.p., 1 H NMR and mass spectrum and a tentative mechanism for its formation is also suggested. A comparison of toxicity of Indole and the oxidation product in albino mice was made by analyzing blood parameters after intracranial injection. The studies clearly suggested that the trimer is more toxic in comparison to Indole.