Structure and absolute stereochemistry of the four N-phenylprotoporphyrin IX regioisomers isolated from phenylhydrazine-treated myoglobin

Swanson, Barbara A.; Montellano, Paul R. Ortiz de

doi:10.1021/ja00021a046

Cited by 38 publications

(28 citation statements)

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“…Extraction of the heme of complex 3 under aerobic conditions by CH,Cl, at pH = 2 (Tuck and Ortiz de Montellano, 1992), followed by an esterification of the carboxylic groups of the heme (White et al, 1981) and zinc insertion, led to a solution absorbing at 442, 552 and 605 nm (data not shown). This spectrum was almost identical to that already described for the dimethyl ester of the zinc-N-phenylprotoporphyrin IX complex (Swanson et al, 1991). These results are similar to those reported for the extraction, under identical conditions, of the heme of a-phenyl complexes of other hemoproteins such as myoglobin (Swanson and Ortiz de Montellano, 1991), hemoglobin (Ringe et al, 1984;Delaforge et al, 1986), cytochrome P450 (Swanson et al, 1991 ;Tuck and Ortiz de Montellano, 1992), catalase (Ortiz de Montellano and Kerr, 1983) and chloroperoxidase (Samokyszyn and Ortiz de Montellano, 1991).…”

Section: Nature Of Complexsupporting

confidence: 84%

“…Such a reaction has also been observed in the case of Hb, Mb (Ttano and Robinson, 1961;Mansuy et al, 1982) and cytochrome P450 (Battioni et al, 1983b;Raag et al, 1990;Swanson et al, 1991;Tuck and Ortiz de Montellano, 1992).…”

Section: Mechanism Of the Reactions Of Pghs Fe(ii1) With Monosubtitutmentioning

confidence: 61%

“…The organic layers were then combined and the esterification of the heme was carried out by addition of 100 pM trimethyloxonium tetrafluoroborate in acetonitrile as described by White et al (1981). After addition of 100 pM zinc acetate at room temperature, the visible spectrum of the sample was recorded and found identical to that previously described for Zn-N-Ph-PPIX Me,E (PPIX Me,E, protoporphyrin IX dimethylester; Swanson and Ortiz de Montellano, 1991).…”

Section: Extraction and Esterification Of The Heme Of The Pghs Fe(ii1mentioning

confidence: 89%

“…The second class is composed of hemeproteins with a relatively wide active site, allowing substrates to interact with the iron atom. This is the case for Hb (Ringe et al, 1984;Delaforge et al, 1986), Mb Ringe et al, 1984;Ortiz de Montellano and Ken;1985), cytochrome P450 (Jonen et a]., 1982; Battioni et al, 1983;Delaforge et al, 1986;Ortiz de Montellano et al, 1983;Raag et al, 1990;Swanson et al, 1991 ;Tuck and Ortiz de Montellano, 1992), catalase (Ortiz de Montellano and Ken;, chloroperoxidase (Samokyszyn and Ortiz de Montellano, 1991) and cytochroine c peroxidase (Ortiz de Montellano, 1992), which all react with monosubstituted hydrazines to give o-alkyl-iron (111) or a-aryl-iron(ll1) complexes. Since our results show that PGHS Fe(II1) reacts with monosubstituted hydrazines with formation of o-alkyl-iron(1II) or o-Ar-iron(ll1) complexes, it is clear that it belongs to that latter class of hemeproteinh and possesses an active site opened wide over the iron atom of the heme.…”

Section: Comparison Between the Different Monosubstituted Hydrazinesmentioning

confidence: 97%

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Reactions of Prostaglandin H Synthase with Monosubstituted Hydrazines and Diazenes

Mahy

Gaspard

Delaforge

et al. 1994

European Journal of Biochemistry

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The reaction of p‐chlorophenylhydrazine with prostaglandin H synthase (PGHS) Fe(III) under aerobic conditions leads to a partial destruction of the heme and to a new complex absorbing at 436 nm. This complex is also obtained by reaction of p‐chlorophenyldiazene (pClPhN = NH) with PGHS Fe(III) under anaerobic conditions and by oxidation of the PGHS Fe(II)(pClPhN = NH) diazene complex by Fe(CN)6K3. The similarity between those reactions and those of arylhydrazines and aryldiazenes with other hemoproteins such as cytochrome P450 and hemoglobin and myoglobin, as well as the similarities between the spectroscopic and chemical properties of this complex and those of the σ‐aryl complexes of other hemoproteins such as hemoglobin and myoglobin, strongly suggested a PGHS Fe(III)‐pClPh structure for this complex. It was completely established after the extraction of its heme, by butan‐2‐one at 0°C under neutral or acidic conditions, which led to the σ‐aryl PGHS‐Fe(III)‐pClPh complex and to N‐phenylprotoporphyrin IX, respectively. A mechanism is proposed for the formation of the PGHS Fe(III) pClPh complex; it includes the reduction of PGHS Fe(III) into PGHS Fe(II) with formation of the diazene pClPhN = NH. This diazene can bind to PGHS Fe(II) or be oxidized with formation of pClPh free radicals. These radicals can react with PGHS Fe(II) to form the PGHS Fe(III)‐pClPh complex or with the protein, or may initiate free radical oxidations which could lead to destruction of the heme or of the protein. Other alkylhydrazines or arylhydrazines also react with PGHS Fe(III) under aerobic conditions with the formation of PGHS Fe(III)‐R or aryl (Ar) complexes and heme destruction. Alkylhydrazines such as methylhydrazine, which lead to very reactive alkyl radicals, lead to very low amounts of PGHS Fe(III)‐R complex and high amounts of heme destruction, whereas arylhydrazines bearing electron‐withdrawing substituents such as 3,4‐dichlorophenylhydrazine, which lead to stabilized aryl radicals, lead to a high amounts of PGHS Fe(III)‐Ar complex and low amounts of heme destruction. Some information concerning the structure of the active site of PGHS has been drawn from those studies as follows: (a) the formation of σ‐aryl PGHS Fe(III)‐Ar and PGHS Fe(II)(ArN = NH) complexes bearing bulky ligands on the iron is in agreement with a large hydrophobic active site with an easily accessible iron atom and, (b) a comparison of the UV‐visible characteristics of PGHS Fe(III)‐R or Ar complexes with those of other hemoprotein‐Fe(III)‐R or hemoprotein‐Fe(III)‐Ar complexes is in agreement with a histidine as the axial proximal ligand of the iron of PGHS. Finally, the formation of iron(III)‐R or iron (III)‐Ar complexes and the free radical oxidative degradation of the heme could both explain why monosubstituted hydrazines are powerful inhibitors of PGHS and very bad reducing cosubstrates of the peroxidase function of PGHS.

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Section: Nature Of Complexsupporting

confidence: 84%

Section: Mechanism Of the Reactions Of Pghs Fe(ii1) With Monosubtitutmentioning

confidence: 61%

Section: Extraction and Esterification Of The Heme Of The Pghs Fe(ii1mentioning

confidence: 89%

Section: Comparison Between the Different Monosubstituted Hydrazinesmentioning

confidence: 97%

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Reactions of Prostaglandin H Synthase with Monosubstituted Hydrazines and Diazenes

Mahy

Gaspard

Delaforge

et al. 1994

European Journal of Biochemistry

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“…In contrast, the catalytic turn( rver of phenylhydrazine by cytochrome P-450 [I 11, haemoglobin [I 21 myoglobin [13] and chloroperoxidase [I41 fails to form the haem edge products typical of peroxidases. Instead, the phenyl radical is directed to the accessible distal haem surface allowing the formation of a spectroscopically distinct iron-phenq 1 com-plex.…”

mentioning

confidence: 99%

Probing the Aromatic‐Donor‐Binding Site of Horseradish Peroxidase Using Site‐Directed Mutagenesis and the Suicide Substrate Phenylhydrazine

Gilfoyle

Rodrı́guez-López

Smith

1996

European Journal of Biochemistry

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The haem groups from two classes of site-directed mutants of horseradish peroxidase isoenzyme C (HRP-C) (distal haem pocket mutants, [H42L]HRP-C* and [R38K]-HRP-C* and peripheral-haem-accesschannel mutants, [F142A]HRP-C* and [F143A]HRP-C*) were extracted and analysed by reverse-phase HPLC after phenylhydrazine-induced suicide inactivation. The relative abundance of the two covalently modified haems, C20-phenyl (8-meso phenyl) and C1 8-hydroxymethyl haem, provided a sensitive topological probe for changes induced in the protein architecture in the vicinity of the haem active site and substrate-access channel. Although differing considerably in their efficiency as peroxidases ([H42L]HRP-C* exhibited only approximately 0.03 % of the peroxidase activity of wild type), the variants studied gave rise to a modification pattern typical of an exposed haem edge thereby strengthening the argument that it is the overall protein topology rather than the intrinsic catalytic activity of the active site that determines the sites of covalent haem modification. Mutants which showed impaired ability to bind the aromatic donor benzhydroxamic acid were less readily modified by the phenyl radical at the haem C18-methyl position although the level of arylation at the haem C20 position remained remarkably constant. Our findings suggest that the overall efficacy of haem modification catalysed by HRP-C during turnover with phenylhydrazine and its vulnerability towards inactivation are related to its general ability to bind aromatic donor molecules. Results from phenylhydrazine treatment of HRP-C wild-type and mutant variants were compared with those obtained for Coprinus cinereus peroxidase, an enzyme which from its structure is known to have a remarkably open access channel to the haem edge. We show evidence that C. cinereus peroxidase is able to bind benzhydroxamic acid, albeit with a relatively high Kd (Kd 3.7 mM), a probe for aromatic-donor binding. We suggest reasons why phenylhydrazine-treated C. cinereus peroxidase was more resistant to haem modification and phenyl-radical-based inactivation than HRP-C.Keywords: horseradish peroxidase; suicide inactivation; phenylhydrazine; site-directed mutagenesis.Classical peroxidases, including horseradish peroxidase (HRP), have been shown to catalyse the transfer of electrons in two distinct one-electron steps from a wide range of aromatic donor molecules [l]. The reaction, initiated by hydrogen peroxide, provides two oxidising equivalents to the resting haem prosthetic group and yields compound I, an oxy-ferryl-[Fe(IV) = 01-based porphyrin radical cation. Although compounds I and 11, the high oxidation state intermediates formed during the catalytic cycle, have been well described [2], continued efforts to understand structure/function relationships in HRP have been hampered by the lack of a high-resolution structure of a class 111 (higher plant) peroxidase. Despite the wealth of biocheniical data for this archetypal peroxidase it has been necessary to rely

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Isocyanurates with Planar Chirality: Design, Optical Resolution, and Isomerization

et al. 2012

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Designs and syntheses of isocyanurates (1-3) are described on the basis of a novel concept that two enantiotopic faces of C(s) -symmetric, prochiral planar molecules are differentiated with a location of groups at the top or bottom of the planar skeleton using a rigid linker. Such isocyanurates are atropisomeric. The planar-chiral structures of 1 and 2(anti) (anti-conformer of 2) were confirmed by single-crystal X-ray analyses, and the space groups were P1 (for 1) and P2(1)/c (for 2(anti)), resulting that the crystals were racemates. Optical resolutions of 1-3 were successfully accomplished by using chiral high-performance liquid chromatography technique in combination with circular dichroism, absorption, and nuclear magnetic resonance spectroscopies and mass spectrometry. Furthermore, the rotational barriers (ΔG(‡)s) related to isomerizations of 1-3 were estimated to be 27.2 (for 1 at 50 °C), 27.6 (for 2(anti) at 50 °C), and 40.6 (for 3(syn) at 150 °C) kcal/mol. The ΔG(‡)s of 2 and 3 were higher than that of 1 and, in particular, that of 3 was highest among them. This result indicates that an introduction of bulky substituents and an intramolecular bridging are effective for inhibitions of the isomerizations.

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Structure and absolute stereochemistry of the four N-phenylprotoporphyrin IX regioisomers isolated from phenylhydrazine-treated myoglobin

Cited by 38 publications

References 1 publication

Reactions of Prostaglandin H Synthase with Monosubstituted Hydrazines and Diazenes

Reactions of Prostaglandin H Synthase with Monosubstituted Hydrazines and Diazenes

Probing the Aromatic‐Donor‐Binding Site of Horseradish Peroxidase Using Site‐Directed Mutagenesis and the Suicide Substrate Phenylhydrazine

Isocyanurates with Planar Chirality: Design, Optical Resolution, and Isomerization

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