Interrelation Between the Catalytic Function of Heme-Proteins and the Structural Modifications of Their Protein Parts

Tsushima, Keizoo; Miyajima, Toshina

doi:10.1093/oxfordjournals.jbchem.a126431

Cited by 14 publications

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“…Although the rate of spontaneous formation of this compound from normal, native ferrihemoglobin is extremely slow, its rate of formation from inherited unstable hemoglobins, hemoglobin H (/3 chain tetramer), and free a and ,B chains is rapid (46,48,49). Globin ferrihemochrome is also formed when oxyhemoglobin or ferrihemoglobin is added to a denaturing medium (46,50). These reactions indicate that instability of a subunit of hemoglobin enables a binding site in the protein component of the subunit to become a ligand of its hemne.…”

Section: Discussionmentioning

confidence: 99%

Ligands and oxidants in ferrihemochrome formation and oxidative hemolysis

Itano

Hirota

Vedvick

1977

Proc. Natl. Acad. Sci. U.S.A.

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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-

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