The meso-reactivity of porphyrins and related compounds. Part V. The meso-oxidation of metalloporphyrins

We have investigated the effect of size of a single neutral ring substituent on the induction of hemolytic anemia and the formation of a ferrihemochrome by substituted phenylhydrazines. The severity of induced anemia decreased with increase in size of a halogen atom or an alkyl group ortho to the hydrazino group, little anemia resulting from 2-iodophenylhydrazine and no anemia from 2-tert-butylphenylhydrazine. The size of a halogen atom or an alkyl group at the meta or para position had relatively little effect on the severity of induced anemia. The ability of an arylhydrazine to induce hemolytic anemia paralleled its ability to produce a ferrihemochrome with an exogenous ligand, probably the corresponding aryldiazene. In general, rapid and complete formation of ferrihemochrome occurred-with arylhydrazines that induced severe anemia. The degree of hemolysis induced by an arylhydrazine was not related to its rate of autooxidation, i.e., the rate at which oxidants are formed by the reduction of oxygen. We propose a mechanism of arylhydrazine-induced oxidative denaturation based on the simultaneous formation of hydroxyl radical and aryldiazene ferrihemochrome in a reaction of oxyhemoglobin with arylhydrazine. We suggest that after oxidation of the porphyrin ring is initiated by a hydroxyl radical, oxidative cleavage of the ring is facilitated by the presence of a large li-

Section: Discussionmentioning

confidence: 68%

Ligands and oxidants in ferrihemochrome formation and oxidative hemolysis

Itano

Hirota

Vedvick

1977

“…4 were previously proposed (1). Oxidation states Fe(II) and Fe(III) have been suggested for the iron atom of III (19,20). We have assigned Fe(II) to III to avoid the complication ofan odd-electron transfer in the formation ofIV, a ferrous compound; reaction 3 requires only 02 (1) and is not known to produce a free radical.…”

mentioning

confidence: 99%

Verdohemochrome IX alpha: preparation and oxidoreductive cleavage to biliverdin IX alpha.

Saito¹,

Itano²

1982

Several studies have shown that both terminal oxygen atoms of biliverdin are derived from molecular oxygen. Since the conversion of verdohemochrome to biliverdin has been assumed to be hydrolytic, these findings seemed to exclude verdohemochrome as an intermediate in the degradation of heme to biliverdin. Coupled oxidation of myoglobin and ascorbate yielded a pure preparation of verdohemochrome IX alpha. The structure and ferrous state of this product were determined from its composition, ligand reactions, 1H NMR spectrum, and conversion to biliverdin IX alpha dimethyl ester. Reaction with ascorbate and 18O2 converted this compound to biliverdin that contained an atom of 18O. Successive treatment of verdohemochrome, first oxidation with H2O2 and then reduction with phenylhydrazine, yielded the iron complex of biliverdin. These results showed that hydrolysis is not an obligatory step in the conversion of verdohemochrome to biliverdin and, moreover, indicated how heme can be converted, with verdohemochrome as an intermediate, into biliverdin in which the two terminal oxygen atoms are derived from different O2 molecules.

“…Phenyl radical from Eqs. 1-3 may add to a pyrrole nitrogen instead of to the -mnwso carbon and result in displacement of the iron atom of heme, which is essential for meso cleavage (19). In the presence of an excess of phenylhydrazine, a second molecule of this compound may react with Fe"H202 (or FeWvO) to restore Fe", aborting ring cleavage and at the same time producing another molecule of phenyldiazene.…”

Section: Discussionmentioning

confidence: 99%

“…A two-electron reduction of oxyhemoglobin (FeI02) was postulated as the initial reaction in coupled oxidation (18). The transient product ofthis reaction, formulated as Fe"H202, Biochemistry: Saito and Itano ochrome was allowed to react with H202 (19). Fe"H202 has also been represented as its anhydro derivative, FeNvO (20).…”

Section: Discussionmentioning

confidence: 99%

See 1 more Smart Citation

beta-meso-Phenylbiliverdin IX alpha and N-phenylprotoporphyrin IX, products of the reaction of phenylhydrazine with oxyhemoproteins.

Saito¹,

Itano²

1981

Oxyhemoglobin and oxymyoglobin were allowed to react aerobically with phenylhydrazine and p-tolylhydrazine. The chloroform extract of each reaction mixture, after treatment with H2SOdmethanol, yielded a blue pigment and a.green pigment, which were identified by electronic absorption, mass, and proton NMR spectroscopy as the dimethyl esters of -mao-arylbiliverdin IXa and N-arylprotoporphyrin IX, respectively. NPhenyiprotoporphyrin IX dimethyl ester formed complexes, with Zn2+, Cd'+, and Hg'+ but not with other cations. The proton NMR spectrum of the zinc complex suggested binding of the phenyl group to one ofthe two pyrrole rings ofprotoporphyrin IX with a propionic acid substitutent. The effectiveness of phenylhydrazine as an inducer of Heinz body formation may be due to destabilization of the hemoglobin. molecule by the replacement of heme with phenyl adducts of biliverdin and protoporphyrin.The green hemoglobin produced in the reaction ofhemoglobin with phenylhydrazine was found by Kiese and Seipelt (1) to differ from verdoglobins produced by other reagents. Lemberg and Legge (2) showed that biliverdin production was increased in the erythrocytes ofrabbits treated with phenylhydrazine, and they concluded that this in vivo result of phenylhydrazine activity corresponded to the in vitro formation ofbiliverdin in the coupled oxidation ofhemoglobin and ascorbic acid. Beaven and White (3), on the other hand, did not obtain biliverdin in the in vitro reaction of phenylhydrazine with oxyhemoglobin; instead they isolated a green pigment with an absorption band in the Soret region suggestive of an intact porphyrin ring.Studies from this laboratory indicated that substituents on the benzene ring affected the hemolytic activity of substituted phenylhydrazine and the binding ofsubstituted phenyldiazenes to methemoglobin in parallel fashion (4). Subsequent studies showed, however, that the hemolytic activity of ring-substituted nitrosobenzenes was not related to their affinities as ligands of deoxyhemoglobin (5).A two-electron transfer to oxyhemoglobin was suggested as the initial step in the degradation ofheme mediated by ascorbic acid (6), and the same transfer was postulated in the reaction of phenylhydrazine with oxyhemoglobin (4). Although the processes may be initiated in the same way, different reported products, biliverdin with ascorbic acid (2) and an intact porphyrin with phenyihydrazine (3), indicate that subsequent steps are different. We therefore undertook to isolate and characterize the products of heme degradation when hemoglobin is treated with arylhydrazines, and we found two types of compounds: one is a biliverdin IXa derivative with an aryl group on a meso carbon, and the other is a protoporphyrin IX derivative with an aryl group on a pyrrole nitrogen.EXPERIMENTAL PROCEDURES Materials and Methods. To a solution of metmyoglobin (5 g, type III from horse heart, Sigma) in potassium phosphate buffer (pH 7.4, 0.01 M, 200 ml), a 50-fold excess of powdered Na2S204 was added under N2. This mixture wa...