<i>In Vitro</i> Porphobilinogen and Porphyrin Synthesis in Thalassemia Major and Sickle Cell Anemia*

Feldman, Felix; Lichtman, Herbert C.

doi:10.1111/j.1749-6632.1965.tb54054.x

Cited by 8 publications

(1 citation statement)

References 10 publications

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“…Zinc protoporphyrin IX (ZnPPIX), present in normal erythrocytes at 0.5-µM concentrations, can elevate above 5-µM concentrations in erythrocyte anemias because of thalassemias, iron deficiency, hemolysis, or chronic inflammatory disease (18)(19)(20). When amounts of bioavailable iron in the reticulocyte are low, the ferrochelatase enzyme inserts zinc into protoporphyrin IX instead of iron, resulting in elevated ZnPPIX in the erythrocyte expressed as a ratio of µmol ZnPPIX to mol of Fe PPIX exceeding the normal value of approximately 25 µmol ZnPPIX to 1 mol FePPIX (19).…”

Section: Introductionmentioning

confidence: 99%

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Iyer¹,

Shi²

2003

Mol. Med.

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The intraerythrocytic Plasmodium falciparum parasite converts most of host hemoglobin heme into a nontoxic heme crystal. Erythrocyte zinc protoporphyrin IX, normally present at 0.5 microM, which is a ratio of 1:40,000 hemes, can elevate 10-fold in some of the anemias associated with malaria disease protection. This work examines a binding mechanism for zinc protoporphyrin IX inhibition of heme crystallization similar to the antimalarial quinolines. Zinc protoporphyrin IX neither forms crystals alone nor extends on preformed heme crystals. Inhibition of both seed heme crystal formation and crystal extension occurs with an inhibitory concentration (IC)50 of 5 microM. Field emission in-lens scanning electron microscopy depicts the transition and inhibition of heme monomer aggregates to heme crystals with and without seeding of preformed hemozoin templates. In vitro zinc protoporphyrin IX, like the quinolines, binds to heme crystals in a saturable, specific, pH, and time-dependent manner. The ratio at saturation is approximately 1 zinc protoporphyrin IX per 250 hemes of the crystal. Unlike the quinolines, zinc protoporphyrin IX binds measurably in the absence of heme. Isolated ring and trophozoite stage parasites have an elevated zinc protoporphyrin IX to heme ratio 6 to 10 times that in the erythrocyte cytosol, which also corresponds to elevated ratios found in heme crystals purified from Plasmodium parasites. This work implicates protection from malaria by a mechanism where elevated zinc protoporphyrin IX in anemic erythrocytes binds to heme crystals to inhibit further crystallization. In endemic malaria areas, severe iron deficiency anemia should be treated with antimalarials along with iron replenishment.

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Section: Introductionmentioning

confidence: 99%

Untitled

Iyer¹,

Shi²

2003

Mol. Med.

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Zinc Protoporphyrin IX Binds Heme Crystals to Inhibit the Process of Crystallization in Plasmodium falciparum

Iyer

Shi

Shankar

et al. 2003

Mol Med

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The intraerythrocytic Plasmodium falciparum parasite converts most of host hemoglobin heme into a nontoxic heme crystal. Erythrocyte zinc protoporphyrin IX, normally present at 0.5 µM, which is a ratio of 1:40000 hemes, can elevate 10-fold in some of the anemias associated with malaria disease protection. This work examines a binding mechanism for zinc protoporphyrin IX inhibition of heme crystallization similar to the antimalarial quinolines. Zinc protoporphyrin IX neither forms crystals alone nor extends on preformed heme crystals. Inhibition of both seed heme crystal formation and crystal extension occurs with an inhibitory concentration (IC) 50 of 5 µM. Field emission in-lens scanning electron microscopy depicts the transition and inhibition of heme monomer aggregates to heme crystals with and without seeding of preformed hemozoin templates. In vitro zinc protoporphyrin IX, like the quinolines, binds to heme crystals in a saturable, specific, pH, and time-dependent manner. The ratio at saturation is approximately 1 zinc protoporphyrin IX per 250 hemes of the crystal. Unlike the quinolines, zinc protoporphyrin IX binds measurably in the absence of heme. Isolated ring and trophozoite stage parasites have an elevated zinc protoporphyrin IX to heme ratio 6 to 10 times that in the erythrocyte cytosol, which also corresponds to elevated ratios found in heme crystals purified from Plasmodium parasites. This work implicates protection from malaria by a mechanism where elevated zinc protoporphyrin IX in anemic erythrocytes binds to heme crystals to inhibit further crystallization. In endemic malaria areas, severe iron deficiency anemia should be treated with antimalarials along with iron replenishment.

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