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Covalent binding of glutathione to hemoglobin. I. Inhibition of hemoglobin S polymerization.

1986; Elsevier BV; Volume: 261; Issue: 31 Linguagem: Inglês

10.1016/s0021-9258(18)66928-5

1083-351X

M.C. Garel, Chantal Domenget, Josiane Caburi-Martin, Claude Préhu, F. Galactéros, Yves Beuzard,

Hemoglobinopathies and Related Disorders

Thiol reagents react with cysteine 893 of hemoglobin and as a result increase the oxygen affinity of hemoglobin.In the present studies we have used a thioldisulfide exchange between mixed disulfides of hemoglobin and reduced glutathione to attach intracellular glutathione to hemoglobin and to study its antisickling properties.The rates of production of glutathionyl hemoglobin (G-Hb) depend on the structure of the thiol reagent linked to cysteine 893.Up to 25% G-Hb can be produced in normal and sickle red cells because of the high intracellular concentration of reduced glutathione.This high level of G-Hb in normal cells increases the oxygen affinity by about 35% and reduces hemeheme interactions.In sickle cells the increased oxygen affinity is associated with an inhibition of sickling of about 70% at 21 mm Hg.Inhibition of polymerization of deoxy HbS is also due to a direct inhibition of intermolecular contacts in the fibers as demonstrated by the increased solubility and the increased delay time of G-HbS compared to deoxy HbS.In spite of growing knowledge of the molecular and cellular lesions leading to sickle cell anemia no specific treatment is at hand.Three approaches to reduce HbS' polymerization in sickle cell anemia have been explored 1) intracellular increase in HbF as obtained recently with 5-azacytidine and hydroxyurea in vivo (1, 2); 2) agents which reduce the dehydration of sickle cells and consequently HbS polymerization, which is highly concentration dependent (3-5); 3) modifying hemoglobin to inhibit directly either the intermolecular contacts within the polymer or indirectly by destabilization of the T (deoxy) state, shifting the Hb conformation toward the R (oxy) state.In all cases the goal is to decrease the concentration of HbS able to polymerize.Reagents affecting HbS can be either covalently or noncovalently bound.Noncovalently bound agents are generally active at concentrations too high to be readily maintained in uiuo.Covalently bound compounds tend to be either not sufficiently specific or overly toxic.However, tailoring com-