The chlorinating activity of human myeloperoxidase: high initial activity at neutral pH value and activation by electron donors

Zuurbier, Karin W.M.; Bakkenist, A.R.J.; Wever, Ron; Muijsers, Anton O.

doi:10.1016/0167-4838(90)90159-d

Cited by 36 publications

(22 citation statements)

References 30 publications

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“…Peripheral neutrophil suspensions had the highest MPO activity detected. MPO is found primarily in the granules of neutrophils [11,13,16,37], and it is suggested to be an indicator of neutrophil accumulation in tissues [13,38] Our findings also confirm that neutrophils are the major source of MPO.…”

supporting

confidence: 77%

Myeloperoxidase Activity in Peripheral Blood, Neutrophil Crevicular Fluid and Whole Saliva of Patients with Periodontal Disease.

Över

Yamalik

Yavuzyilmaz

et al. 1993

The Journal of Nihon University School of Dentistry

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supporting

confidence: 77%

Myeloperoxidase Activity in Peripheral Blood, Neutrophil Crevicular Fluid and Whole Saliva of Patients with Periodontal Disease.

Över

Yamalik

Yavuzyilmaz

et al. 1993

The Journal of Nihon University School of Dentistry

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“…The reason for this discrepancy is that our measurements were recorded over the first 10 s of the reaction where myeloperoxidase has lost considerable activity compared with that in the first few milliseconds [42]. Our value for the catalytic rate constant for chloride is similar to that of 25 s −" measured previously after 1 s of reaction [42]. Thus the specificity constants in Table 1 do not represent the true rate constants for the reactions of compound I.…”

Section: Discussionmentioning

confidence: 60%

“…However, the value of k Cl − is considerably less than the rate constant of (4n7p0n1)i10' M −" :s −" for the reaction of chloride with compound I, which was obtained by pre-steady-state stopped-flow measurements [41]. The reason for this discrepancy is that our measurements were recorded over the first 10 s of the reaction where myeloperoxidase has lost considerable activity compared with that in the first few milliseconds [42]. Our value for the catalytic rate constant for chloride is similar to that of 25 s −" measured previously after 1 s of reaction [42].…”

Section: Discussionmentioning

confidence: 65%

Thiocyanate and chloride as competing substrates for myeloperoxidase

Dalen

Whitehouse

Winterbourn

et al. 1997

Biochemical Journal

382

293

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The neutrophil enzyme myeloperoxidase uses H2O2 to oxidize chloride, bromide, iodide and thiocyanate to their respective hypohalous acids. Chloride is considered to be the physiological substrate. However, a detailed kinetic study of its substrate preference has not been undertaken. Our aim was to establish whether myeloperoxidase oxidizes thiocyanate in the presence of chloride at physiological concentrations of these substrates. We determined this by measuring the rate of H2O2 loss in reactions catalysed by the enzyme at various concentrations of each substrate. The relative specificity constants for chloride, bromide and thiocyanate were 1:60:730 respectively, indicating that thiocyanate is by far the most favoured substrate for myeloperoxidase. In the presence of 100 mM chloride, myeloperoxidase catalysed the production of hypothiocyanite at concentrations of thiocyanate as low as 25 μM. With 100 μM thiocyanate, about 50% of the H2O2 present was converted into hypothiocyanite, and the rate of hypohalous acid production equalled the sum of the individual rates obtained when each of these anions was present alone. The rate of H2O2 loss catalysed by myeloperoxidase in the presence of 100 mM chloride doubled when 100 μM thiocyanate was added, and was maximal with 1 mM thiocyanate. This indicates that at plasma concentrations of thiocyanate and chloride, myeloperoxidase is far from saturated. We conclude that thiocyanate is a major physiological substrate of myeloperoxidase, regardless of where the enzyme acts. As a consequence, more consideration should be given to the oxidation products of thiocyanate and to the role they play in host defence and inflammation.

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“…For example, in the red alga Corallina pilulifera, the optimum H 2 O 2 concentration for the V-enzyme activity ranged between 0.5 and 5 mM, the enzyme being inhibited at higher concentrations (Itoh et al 1986). Heme-containing peroxidises, on the other hand, are reported to be inhibited at lower H 2 O 2 concentrations (Zuurbier et al 1990). The heme type haloperoxidase of the red microalga Porphyridium purpureum was inhibited at H 2 O 2 concentrations above 0.1 mM (Murphy et al 2000), as it also was observed in this study for A. taxiformis.…”

Section: Discussionmentioning

confidence: 98%

Effects of hydrogen peroxide on the content of major volatile halogenated compounds in the red alga Asparagopsis taxiformis (Bonnemaisoniaceae)

et al. 2010

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The genus Asparagopsis is a prolific source of halogenated metabolites. Due to its commercial applications, it has been intensively cultivated in southern Portugal. In the present study, we assess if the internal levels of the major halogenated metabolites (bromoform and dibromoacetic acid) in Asparagopsis taxiformis can be increased with hydrogen peroxide (H 2 O 2 ) addition. Previous studies with red algae showed that the production/release of bromoform can be enhanced by exogenously supplying H 2 O 2 . However, no study has assessed if H 2 O 2 supply enhances the content of secondary metabolites within the biomass. This detail is important as the objective of the proposed research is to enhance the content of these valuable metabolites in the produced biomass. Both the activity of the haloperoxidase enzyme and the metabolite content were assessed on shortterm and long-term incubation periods to H 2 O 2 . To determine the susceptibility of A. taxiformis photosynthetic performance to the imposed oxidative stress, the in vivo fluorescence of photosystem II was monitored. A. taxiformis was shown to be physiologically vulnerable to H 2 O 2 , given the observed decrease of the maximum quantum yield of photosynthesis (F v /F m ). Contrary to what was expected, the presence of H 2 O 2 inhibited the activity of the iodoperoxidase enzyme. Nevertheless, the extracted halogenated metabolites were higher over the first hours of exposure to H 2 O 2 , decreasing after 48 h. These results are probably related to the prosthetic group of the halogenated enzyme in A. taxiformis and the long-term oxidative stress damage of H 2 O 2 exposure. Considering the objective of the proposed research, addition of H 2 O 2 to the cultures, prior (3 h) to biomass harvesting, increases the metabolite content.

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The chlorinating activity of human myeloperoxidase: high initial activity at neutral pH value and activation by electron donors

Cited by 36 publications

References 30 publications

Myeloperoxidase Activity in Peripheral Blood, Neutrophil Crevicular Fluid and Whole Saliva of Patients with Periodontal Disease.

Myeloperoxidase Activity in Peripheral Blood, Neutrophil Crevicular Fluid and Whole Saliva of Patients with Periodontal Disease.

Thiocyanate and chloride as competing substrates for myeloperoxidase

Effects of hydrogen peroxide on the content of major volatile halogenated compounds in the red alga Asparagopsis taxiformis (Bonnemaisoniaceae)

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