Isolation procedure and some properties of myeloperoxidase from human leucocytes

Bakkenist, A.R.J.; Wever, Ron; Vulsma, Thomas; Plat, H.; Gelder, B.F. Van

doi:10.1016/0005-2744(78)90101-8

Cited by 184 publications

(78 citation statements)

References 26 publications

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“…Human myeloperoxidase was isolated from human leukocytes as previously described [18]. The A428 n m / A 2 8~ nm ratios of the enzyme preparations used in this study were…”

Section: Methodsmentioning

confidence: 99%

Reaction of myeloperoxidase with its product HOCI

Floris

Wever

1992

European Journal of Biochemistry

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The reaction of human myeloperoxidase with its product, hypochlorous acid was investigated using both rapid-scan spectrophotometry and the stopped-flow technique. In the reaction of myeloperoxidase with hypochlorous acid a primary compound is found with properties similar to that of compound I and which is converted into compound 11. The primary reaction is strongly pHdependent. At pH 7.2 the reaction is too fast to be measured but at higher pH values it is possible to determine the apparent second-order rate constant. Its value decreases to about 2 x lo7 M-' . s-' at pH 8.3 and to 2.3 (+0.4) x lo6 M -l . s-' at pH 9.2, respectively. The dissociation constant for the formation of the primary compound is 25.7 (f 15.3) pM at pH 9.2 and about 2.5 pM at pH 8.3. The apparent second-order rate constant for the formation of compound I1 is hardly affected by pH and varies between 2 to 5 x lo4 M-' . s-' at pH 10.2 and pH 8.3, respectively.Reaction of myeloperoxidase with hypochlorous acid also resulted in irreversible partial bleaching of the chromophore. Chloride, which is a substrate of the enzyme not only protects myeloperoxidase against bleaching by hypochlorous acid but also competitively inhibits the binding of hypochlorous acid to myeloperoxidase, a process which also has been observed in the reaction with hydrogen peroxide. It is concluded that hypochlorous acid binds at the heme iron to form compound I.Myeloperoxidase (donor :hydrogen peroxide oxidoreductase) is a heme-containing enzyme found in the primary granules of human neutrophils. Because of the unique ability of the enzyme to catalyze the H20z-dependent peroxidation of C1-to HOCI, which is an anti-microbial agent, myeloperoxidase is thought to play an important role in the killing of micro-organisms [I, 21. Several spectroscopically distinguishable forms of myeloperoxidase are known : native enzyme, compounds I, I1 and 111. The first step in the peroxidation of chloride is the reaction of myeloperoxidase with hydrogen peroxide to form compound I [3 -51. Compound I is a short-living intermediate in which the prosthetic group is in an oxidized state which is two oxidation equivalents above the ground state. Compound I is very reactive and able to oxidize chloride to hypochlorous acid. The formation of compound I is a very fast process, the apparent second-order rate constant being 2.3 x lo7 M -' . s- ' [5]. The reaction is pHdependent and its rate is governed by a group which, when protonated, prevents H2O2 from binding to myeloperoxidase. The pK, of this group is 4.3 and it has been suggested that the distal histidine with this pK, governs the binding of H2O2 to the enzyme [5, 61.Chloride is able to inhibit the binding of H z 0 2 to myeloperoxidase competitively [5, 7 -101. This process is governed by the same acid/base equilibrium. However, in contrast to H202, chloride binds to the heme iron when the protonatable group is protonated.Reaction of compound I with reductants, such as D-penicillamine [lf], ferrocytochrome c (121 and also hydrogen peroxide [1...

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“…Human myeloperoxidase was isolated from human leukocytes as previously described [18]. The A428 n m / A 2 8~ nm ratios of the enzyme preparations used in this study were…”

Section: Methodsmentioning

confidence: 99%

Reaction of myeloperoxidase with its product HOCI

Floris

Wever

1992

European Journal of Biochemistry

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“…1 B). The subtle differences in apparent molecular mass of the immunoreactive protein may reflect the presence of myeloperoxidase isozymes (60)(61)(62). All 14 atherosclerotic arteries examined by Western blotting contained immunoreactive myeloperoxidase.…”

mentioning

confidence: 99%

Myeloperoxidase, a catalyst for lipoprotein oxidation, is expressed in human atherosclerotic lesions.

et al. 1994

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“…The fact that nitrite is a strong field ligand suggests that, as proposed by Lukat et al [13] this complex is Fe3*/'NO.;. However, the same EPR signals are seen as a minor low-spin component of some myeloperoxidase [23][24][25] and spleen green haemoprotein preparations [26]. Either nitrite is not a haem ligand in these species or these preparations have some nitrite-bound enzyme as purified.…”

Section: Discussionmentioning

confidence: 99%

“…However, our confirmation of this observation (and similar results with the enzyme as purified and with lfitrite) confirms a small, but significant, difference in the EPR spectra of isoenzyme 1. The differences between the spectra of isoenzyme I and isoenzj, mes I1/111 are very unlikely to be due to a change in the ligand at the active site; howeveL they may be responsible for some of the differences seen in the high-spin EPR spectra as prepared by different authors [7~18, [23][24][25]. It is interesting that the isoenzyme with distinct substrate reactivity [7] is also that with distinct EPR spectra, althotlgh whether these two observations are linked to the same physical difference remains to be determined.…”

Section: Discussionmentioning

confidence: 99%

Interaction of human myeloperoxidase with nitrite

Cooper

Odell

1992

FEBS Letters

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EPR (el~.'~tron paramagnetic re.~onance) and optical spectroscopy show that human neutropllil myeloperoxida~e is converted from ferric high-spin to low-spin by the addition of nitrite. The Soret peak shifts from 429 to 447 nm and new peaks appear in the visible re~ion at 573 and 627 am; the EIaR g.values change from 6.84, 5.02, 1.95 to 2.55, 2.31, 1.82. Small dilTerenee~ are seen in the EPR (but, not optical) ~pectra of myeloperoxidase isoenzyme i compared to isoenzymes I1 and II1. The reaction with nitrite is detectable by EPR in intact neutrophils and is thus a lao~sible in vivo monitor of NO/nitrite production by these cells.

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Isolation procedure and some properties of myeloperoxidase from human leucocytes

Cited by 184 publications

References 26 publications

Reaction of myeloperoxidase with its product HOCI

Reaction of myeloperoxidase with its product HOCI

Myeloperoxidase, a catalyst for lipoprotein oxidation, is expressed in human atherosclerotic lesions.

Interaction of human myeloperoxidase with nitrite

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