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D Metodiewa

Publications and source records attributed to D Metodiewa.

At least 37 records · Page 2Linked to original sources
PubMed1991

3-Aminotriazole is a substrate for lactoperoxidase but not for catalase.

Rapid scan spectrophotometry has been applied to investigate the reaction of 3-aminotriazole with mammalian heme enzymes, represented by lactoperoxidase and bovine liver catalase. The results clearly indicate that 3-aminotriazole is a substrate for lactoperoxidase compounds I, II and III, but it does not convert catalase compound I to II under conditions favoring peroxidatic activity of the enzyme. The possible physiological significance of these findings is discussed.

Amitrole↗
PubMed1991

The activity of mammalian peroxidases (lactoperoxidase and myeloperoxidase) and their compounds III toward 2-t-butyl-4-methoxyphenol (butylated hydroxyanisole) and its dimer (2,2'-dihydroxy-3,3'-di-t-butyl-5,5'-dimethoxydiphenyl).

Spectral evidence is presented which shows that butylated hydroxyanisole (BHA) and its dimer act as electron donors for lactoperoxidase (LPO) and myeloperoxidase (MPO) by two different pathways: peroxidative and oxidative. LPO compound II and MPO compound II are converted to native enzymes in their reactions with BHA without detectable intermediates. This confirms a normal peroxidatic oxidation of this commonly used antioxidant. We also report spectral data indicating the reductions of peroxidase compound III to the native state in reactions with BHA (LPO, MPO) or with di-BHA (LPO). This oxidative reaction has significant physiological relevance, ensuring return of peroxidases to the native state for re-entry into the normal peroxidatic cycle or into halogenating reactions.

Biotransformation↗
PubMed1991

On the ability of lactoperoxidase to catalyze the peroxidase-oxidase oxidation of a vitamin E water-soluble derivative (Trolox C).

The rapid-scan spectral technique has been applied to test conversion of the lactoperoxidase compounds during the peroxidase-oxidase catalyzed oxidation of Trolox. The results clearly indicate a normal peroxidatic pathway of Trolox degradation. Changes of spectral scan profiles were investigated to study directly the interaction of Trolox with lactoperoxidase compound III. Oxygen radicals were not involved in peroxidase-mediated oxidation of Trolox. The rate of the one-electron reduction of lactoperoxidase compound I to II was the same in the absence and presence of equal amounts of Trolox and ascorbic acid, which is also a good substrate for lactoperoxidase. The oxidation of Trolox by lactoperoxidase has potential physiological relevance. Since it could help maintain the catalytic cycles and activity of animal peroxidases, leading to detoxification of hydrogen peroxide as a main product of inflammation processes.

Ascorbic Acid↗
PubMed1991

Involvement of lactoperoxidase in the peroxidative degradation of serotonin: a potential pathway for indolaminergic melanin formation.

The peroxidase-catalyzed degradation of 5-hydroxytryptamine (serotonin) was studied using rapid scan or conventional spectrophotometry for detection of one-electron conversions of enzyme compounds I, II and III. The spectral changes of serotonin during oxidation and spectral and bleaching properties of reaction products were examined. The results of the investigation clearly indicate the ability of serotonin to function as an electron donor substrate for animal peroxidases.

Hydrogen Peroxide↗
PubMed1990

The role of myeloperoxidase in the oxidation of biologically active polyhydroxyphenols (substituted catechols).

The reaction of myeloperoxidase with biologically active polyhydroxyphenols (substituted catechols): catecholamine, norepinephrine and 2,4,5-trihydroxyphenylalanine [Phe(OH)3] were investigated by using the ESR spin-stabilization technique and rapid-scan spectrophometry in the millisecond time scale. The results presented here indicate that dihydroxyphenols and trihydroxyphenols are substrates in the myeloperoxidase reaction. The data of ESR and rapid-scan optical investigation of the myleoperoxidase reaction with the dihydroxyphenols catecholamine and norepinephrine clearly indicate a normal peroxidase-type pathway of catecholamine degradation. The first evidence of o-semiquinone radical formation as a product of the enzymatic oxidation of catecholamine by myeloperoxidase is reported. The results obtained by rapid-scan spectrophotometric investigation of enzyme intermediate formation and decay showed qualitative agreement with the spin-stabilization studies. The first results on the reaction of myeloperoxidase with the trihydroxyphenol Phe(OH)3 presented here, indicate that it plays a role as an electron donor for myeloperoxidase I, but we were unable to obtain evidence that a normal peroxidase cycle is occurring. The inhibitory effect of superoxide dismutase on product formation was evident and indicate the involvement of superoxide radicals in the process. Attention is drawn to the biochemical and toxicological implications of these and other related studies of substituted catechol peroxidation by mammalian peroxidases.

Animals↗
PubMed1990

Evidence for one-electron oxidation of benzylpenicillin G by lactoperoxidase compounds I and II.

The ability of the widely used antibiotic benzylpenicillin G to undergo a peroxidatic oxidation to produce free radical species has been investigated using conventional spectrophotometry, rapid scan spectrophotometry and an ESR spin trapping technique. Lactoperoxidase was used as a model for a drug oxidizing system. The results of the investigation indicate a normal peroxidatic pathway of benzylpenicillin degradation which leads to superoxide radical generation.

Electron Spin Resonance Spectroscopy↗
PubMed1990

One-electron reduction of chloroperoxidase by radiolytically generated electrons.

Upon irradiation of aqueous ethylene glycol/water solutions of native chloroperoxidase (CPO) with 60Co-gamma rays at 77K one observes the one-electron reduction of the enzyme active site by radiolytically generated thermolyzed electrons. In the present study the first absorption spectrum of a low-spin ferrous form of CPO is reported which has peaks at 438, 532 and 563 nm, similar to those observed previously for cytochrome P-450. All previously described ferrous forms of CPO are high spin. In order to observe the final results of the CPO reaction with electrons, the spectral changes of native enzyme after room temperature-gamma-irradiation have also been investigated. Evidence of changes is also presented probably connected with disruption of the tertiary structure of enzyme, correlated with decrease of enzyme activity.

Chloride Peroxidase↗
PubMed1989

Oxidation of the substituted catechols dihydroxyphenylalanine methyl ester and trihydroxyphenylalanine by lactoperoxidase and its compounds.

The reactions of native lactoperoxidase and its compound II with two substituted catechols have been investigated by ESR spin stabilization and spin trapping and by rapid scan and conventional spectrophotometric techniques. The catechols are Dopa methyl ester (dihydroxyphenylalanine methyl ester) and 6-hydroxy-Dopa (trihydroxyphenylalanine). o-Semiquinone radicals are formed in the anaerobic reaction of Dopa methyl ester with hydrogen peroxide catalyzed by native lactoperoxidase. The comparable anaerobic reaction of 6-hydroxy-Dopa appears to produce hydroxyl radicals in an unusual reaction. Compound II is reduced back to native lactoperoxidase by both catechols. The reaction between Dopa methyl ester and compound II undergoes an oscillation. The results on the overall lactoperoxidase cycle indicate two successive one-electron reductions of the peroxidase intermediates back to the native enzyme. The resulting free radical formation of o- and p-semiquinones and subsequent formation of stable quinones and Dopachromes is dependent upon the stereochemical arrangement of the catechol hydroxyl groups.

Catechol Oxidase↗
PubMed1989

Evidence for a peroxidatic oxidation of norepinephrine, a catecholamine, by lactoperoxidase.

The electron spin resonance-spin stabilization technique has been applied to identify the o-semiquinone intermediate produced during the lactoperoxidase-catalyzed oxidation of the catecholamine norepinephrine. The results of a rapid scan and spectrophotometric investigation of the reaction clearly indicate a normal peroxidatic pathway of catecholamine degradation.

Benzoquinones↗
PubMed1989

The reactions of chloroperoxidase in the presence of xanthine/xanthine oxidase.

Spectral data are presented which indicate that chloroperoxidase is converted to compound II during the reaction with superoxide/hydrogen peroxide generated in the xanthine/xanthine oxidase system. Upon completion of compound II formation, compound II returns back to the native state of chloroperoxidase without formation of detectable intermediates. It is shown that chloroperoxidase acts as a superoxide scavenger but less effectively than superoxide dismutase. Addition of chloride ion enhances the rate of decay of compound II to native enzyme, showing that chloride ion is oxidized to a chlorine atom in the presence of compound II.

Chloride Peroxidase↗
PubMed1989

The reactions of horseradish peroxidase, lactoperoxidase, and myeloperoxidase with enzymatically generated superoxide.

The formation and decay of intermediate compounds of horseradish peroxidase, lactoperoxidase, and myeloperoxidase formed in the presence of the superoxide/hydrogen peroxide-generating xanthine/xanthine oxidase system has been studied by observation of spectral changes in both the Soret and visible spectral regions and both on millisecond and second time scales. It is tentatively concluded that in all cases compound III is formed in a two-step reaction of native enzyme with superoxide. The presence of superoxide dismutase completely inhibited compound III formation; the presence of catalase had no effect on the process. Spectral data which indicate differences in the decay of horseradish peroxidase compound III back to the native state in comparison with compounds III of lactoperoxidase and myeloperoxidase are also presented.

Catalase↗
PubMed1989

Pulse radiolysis of catalase in solution. I. Reactions of O2- with catalase and its compound I.

The time-course of absorption changes of oxygen-saturated solutions of bovine-liver catalase after pulse radiolysis have been studied. The rate constant of formation of Compound I due to the reaction of catalase with hydrogen peroxide has been estimated to be 2.0 x 10(7) dm3mol-1s-1. Radiation generated superoxide radicals reduce Compound I to Compound II with a rate constant of 5.0 x 10(6) dm3mol-1s-1. The formation of Compound III in the direct reaction of O2- with catalase has also been observed.

Animals↗
PubMed1980

ESR studies on oxidation state changes of copper in superoxide dismutase during reactions with water radiolysis products at cryogenic temperatures.

Irradiating the aqueous solutions of native and reduced superoxide dismutase with 60Co gamma-rays at 77 K and recording the ESR spectra during thermal annealing the formation and decay of the complexes E-Cu2+...HO2 and E-Cu+...HO2 have been observed. Decay of ESR signals corresponding to HO2 in these complexes is not accompanied by immediate changes of the oxidation state of copper. The delayed changes of copper oxidation state are probably due to the reactions of dismutation products with superoxide dismutase.

Animals↗