Formation of nitrosothiols by the reaction of different forms of hemoglobin with (tetranitrosyl)bis(pyrimidin-2-ylthio)diiron |
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| Authors: | L A Syrtsova N A Sanina N I Shkondina E S Chudinova N S Emel’yanova A I Kotel’nikov S M Aldoshin |
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| Institution: | (1) Department of Biochemistry, S.B. S.P.G. Institute of Biomedical Sciences and Research, Balawala, Dehradun, Uttarakhand, 248161, India;(2) Department of Biochemistry, Oman Medical College, P.O. Box 391, Sohar, Oman |
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| Abstract: | The reaction of hemoglobin (Hb), oxyhemoglobin (HbO2), and methemoglobin (metHb) with the tetranitrosyl iron complex of the fu2-S type Fe2(SC4H3N2)2(NO)4] (1) was studied. The reaction results in the nitrosylation of the free SH group of 93-β-cysteine in these forms of hemoglobin.
The change in the Hb, HbO2, and metHb concentrations was monitored by spectrophotometry, recording the difference absorption spectra of the experimental
systems with these forms of hemoglobin and the buffer containing complex 1 in the same concentration. The absorption spectra
were processed to obtain the components using the MATHCAD method. The nitrosothiol concentration was determined by the Saville
reaction. In a protic medium containing 3.3% DMSO, complex 1 spontaneously generates NO due to hydrolysis (k = 3.7 · 10-4 s-1). Oxyhemoglobin reacts with evolved NO to form metHb. Complex 1 reduces metHb with a high rate to yield Hb (k = 6.7 · 10-3 s-1) followed by the formation of HbNO (k = 6.5 · 10-3 s-1). Oxidized complex 1 yields NO with a higher rate than the starting complex does. The reaction of HbO2 and metHb (0.02 mmo1 L-1) with complex 1 affords nitrosothiols in micromolar concentration during 5 min, and no nitrosothiol is formed in the case
of Hb. |
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