Effect of hydroxyl radical scavengers on microsomal oxidation of alcohols and on associated microsomal reactions

Cederbaum, Arthur I.; Dicker, Elisa; Cohen, Gerald

doi:10.1021/bi00608a018

Cited by 82 publications

(56 citation statements)

References 37 publications

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“…The formation of aminopyrine free radical is directly confirmed by optical and ESR spectroscopic methods in cytochrome P450 reactions (99,100). The involvement of free radical intennediate is also confirmed with the uses ofspin traps (101)(102)(103) and radical scavengers (103)(104)(105). Particularly, several workers have concluded that the hydroxyl radical which is formed through an ironcatalyzed Haber-Weiss reaction causes the hydroxylation of aniline (106) and benzene (107), and the oxidation of ethanol (108)(109)(110)(111).…”

Section: Enzymatic Formation Of Free Radicalsmentioning

confidence: 81%

Physiological Aspects of Free-Radical Reactions

Yamazaki¹,

Tamura²,

Nakajima³

et al. 1985

Environmental Health Perspectives

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Enzymes which catalyze the formation of free radicals in vitro will catalyze similar reactions in vivo. We believe that the formation of some kinds of free radicals has definite physiological meanings in metabolism. In this sense, the enzymes forming such free radicals are concluded to be in evolutionally advanced states. Elaborated structure and function of enzymes such as horseradish peroxidase and microsomal flavoproteins support the idea. Deleterious and side reactions caused by free radicals are assumed to be minimized in vivo by localizing the reactions, but this assumption should be verified by future studies.

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Section: Enzymatic Formation Of Free Radicalsmentioning

confidence: 81%

Physiological Aspects of Free-Radical Reactions

Yamazaki¹,

Tamura²,

Nakajima³

et al. 1985

Environmental Health Perspectives

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“…It is interesting to note that outside the field of nitrification, thiourea and alkyl derivatives are actually regarded as extremely nonspecific ligands that can form complexes with more than 70 ionic species (24). More recently, thiourea has been shown to act as a potent scavenger of both hydroxyl and superoxide radicals in biological systems (7,19); monooxygenase-catalyzed reactions may involve these reactive intermediates. Perhaps the inhibition of AMO by CS2 (and related compounds) provides more convincing evidence for a role for copper in AMO than is provided by the inhibition by thiourea and its derivatives.…”

Section: Resultsmentioning

confidence: 99%

Inhibition of ammonia monooxygenase in Nitrosomonas europaea by carbon disulfide

1990

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Carbon disulfide has long been recognized as a potent inhibitor of nitrification, and it is the likely active component in several nitrification inhibitors suitable for field use. The effects of this compound on Nitrosomonas europaea have been investigated, and the site of action has been determined. Low concentrations of CS2 (<400 ,uM) produced a time-dependent inhibition of ammonia-dependent O2 uptake but did not inhibit hydrazineoxidizing activity. CS2 also produced distinct changes in difference spectra of whole cells. These results suggest that ammonia monooxygenase (AMO) is the site of action of CS2. Unlike the case for thiourea and acetylene, saturating concentrations of CS2 did not fully inhibit AMO, and the inhibition resulted in a low but significant rate of ammonia-dependent 02 uptake. The effects of CS2 were not competitive with respect to ammonia concentration, and the inhibition by CS2 did not require the turnover of AMO to take effect. The ability of CS2-treated cells to incorporate [14C]acetylene into the 28-kilodalton polypeptide of AMO was used to demonstrate that the effects of CS2 are compatible with a mode of action which involves a reduction of the rate of turnover of AMO without effects on the catalytic mechanism. It is proposed that CS2 may act on AMO by reversibly reacting with a suitable nucleophilic amino acid in close proximity to the active site copper.The major process in microbial nitrification is the oxidation of ammonia to nitrite, followed by the oxidation of nitrite to nitrate. These reactions are predominantly catalyzed by specialized autotrophic bacteria characterized by such species as the ammonia-oxidizing bacterium Nitrosomonas europaea and the nitrite-oxidizing bacterium Nitrobacter winogradskyi, respectively. Although our understanding of the biochemistry and enzymology of individual reactions in the nitrification process is far from complete, there is a considerable general interest in nitrification because it plays an important role in controlling the balance between fixed and mobile forms of nitrogen in soil and water systems. For example, in agriculture, nitrification can lead to substantial losses of costly ammonia-based fertilizer (and urea-based fertilizer, which hydrolyzes to ammonia) because both nitrification products, nitrite and nitrate, are easily leached from soils by water. In addition, nitrate is the major substrate for denitrifying bacteria that generate gaseous products (N20, NO, and N2) which are lost to the atmosphere. These same reactions, while detrimental to agriculture, are regarded as positive benefits in water treatment regimens, in which the objective is to reduce the nitrogen content of waste waters (22).Because it is ammonia-oxidizing bacteria that initiate nitrification as a whole, there has been considerable research into the inhibition of this process. Ammonia oxidation by N. europaea is a two-stage process that is now thought to involve the initial oxidation of ammonia to hydroxylamine by a membrane-bound enzyme known as ammonia monooxyge...

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“…These studies were performed in complete HBSS, at or near physiologic pH and using previously identified scavengers in concentrations that did not decrease cell viability or phagocytosis (6)(7)(8)(9)(10)(36)(37)(38)(39). Additional studies showed that DMSO, thiourea and urea did not inhibit phagocytosis of radiolabeled bacteria by PMN (40) or decrease the ability of phagocytes to exclude trypan blue.…”

Section: Methodsmentioning

confidence: 99%

Generation of Hydroxyl Radical by Enzymes, Chemicals, and Human Phagocytes In Vitro

Repine¹,

Eaton²,

Anders³

et al. 1979

J. Clin. Invest.

265

101

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A B S T R A C T Methane (CH4) production from the anti-inflammatory agent, dimethyl sulfoxide (DMSO), was used to measure *OH from chemical reactions or human phagocytes. Reactions producing * OH (xanthine/xanthine oxidase or Fe++/EDTA/H202) generated CH4 from DMSO, whereas reactions yielding primarily 0r or H202 failed to produce CH4. Neutrophils (PMN), monocytes, and alveolar macrophages also produced CH4 from DMSO. Mass spectroscopy using cJ-DMSO showed formnation of d3-CH, indicating that CH4 was derived from DMSO. Methane generation by normal but not chronic granulomatous disease or heat-killed phagocytes increased after stimulation with opsonized zymosan particles or the chemical, phorbol myristate acetate. Methane production from DMSO increased as the number of stimulated PMN was increased and the kinetics of CH4 production approximated other metabolic activities of stimulated PMN. Methane production from stimulated phagocytes and DMSO was markedly decreased by purportedly potent -OH scavengers (thiourea or tryptophane) and diminished to lesser degrees by weaker -OH scavengers (mannitol, ethanol, or Indeed, stimulated neutrophils (PMN), monocytes (MN) or alveolar marcophages (AM) do produce C2H4 from methional or KMB (6-10). However, the strict dependence of C2H4 production upon -OH is in doubt (8,(10)(11)(12)(13)(14). Methional spontaneously forms C2H4, especially during prolonged incubations with tissues (8), and can also react with H202 to form C2H4 (10). The specificity of KMB as a detector of -OH is also in question because C2H4 production from KMB may reflect, at least in part, reactions with 02 or hypochlorous acid (10).In Ca++ and Mg++ (26). Contaminating erythrocytes were lysed by adding 6 ml of ice-cold sterile distilled water and mixing gently for 35 s. Tonicity was rapidly restored with 2 ml of hypertonic (4x) Ca++ and Mg++ free HBSS. The mixture was then centrifuged at 170 g for 10 min. Cells in the pellet were then washed once more, resuspended in HBSS with Ca++ and Mg++, counted, and used immediately. PMN preparations contained >98% PMN with only a few lymphocytes and rare erythrocytes, platelets or MN. Suspensions of MN were similarly prepared. The percentages of MN were determined by differential counting of 600 cells on Wright's stained smears and cytochemically confirmed by esterase stain. MN preparations contained -30% MN, <1% PMN, and the remainder lymphocytes. AM were obtained by bronchoscopic sterile saline lavage of the unaffected subsegments of the lungs of patients undergoing evaluations for localized pulmonary disease or from healthy volunteers (9). AM were recovered from lavage fluids, washed once, and counted. The final preparations contained >90% AM and <2% PMN. More than 85% of the AM excluded trypan blue. Concentrations of lymphocytes or platelets that were comparable to those remaining in phagocyte preparations did not produce significant amounts of CH4 from DMSO.Preparation of pooled human serum, opsonized zymosan, or PMA. Pooled human serum was prepared from clotted ...

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Effect of hydroxyl radical scavengers on microsomal oxidation of alcohols and on associated microsomal reactions

Cited by 82 publications

References 37 publications

Physiological Aspects of Free-Radical Reactions

Physiological Aspects of Free-Radical Reactions

Inhibition of ammonia monooxygenase in Nitrosomonas europaea by carbon disulfide

Generation of Hydroxyl Radical by Enzymes, Chemicals, and Human Phagocytes In Vitro

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