Effect of bezafibrate and clofibric acid on the spectroscopic properties of the nitric oxide derivative of ferrous human hemoglobin.
The effect of bezafibrate (BZF) and clofibric acid (CFA) on the spectroscopic (EPR and absorbance) properties of the nitric oxide derivative of ferrous human hemoglobin (HbNO) has been investigated quantitatively. In the presence of BZF and CFA, the X-band EPR spectra and the absorption spectra in the Soret region of HbNO display the same basic characteristics described in the presence of inositol hexakisphosphate (IHP) and 2, 3-diphosphoglycerate (2,3-DPG). Next, in the presence of these allosteric effectors, the oxygen affinity for ferrous human hemoglobin (Hb) is reduced. These findings indicate that BZF and CFA, as already reported for IHP and 2, 3-DPG, induce the stabilization of a low affinity conformation of the ligated hemoprotein (i.e., HbNO). Values of the apparent equilibrium constant for BZF and CFA binding to HbNO (K) are 1.5(+/- 0.2) x 10(-2) M and 2.8(+/- 0.3) x 10(-2) M, respectively, at pH 7.0 (in 0.1 M N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid]/NaOH buffer system plus 0.1 M NaCl) and 20 degrees C. The results reported here represent clearcut evidence for BZF and CFA specific (i.e., functionally relevant) binding to a ligated derivative of Hb (i.e., HbNO).
Ascenzi
P
P
Department of Pharmaceutical Chemistry and Technology, University of Turin, Italy.
Coletta
M
M
Desideri
A
A
Polizio
F
F
Bertollini
A
A
Santucci
R
R
Amiconi
G
G
D019794:2,3-Diphosphoglycerate; D001629:Bezafibrate / Q000494:pharmacology*; D002995:Clofibric Acid / Q000494:pharmacology*; D004163:Diphosphoglyceric Acids / Q000494:pharmacology; D004578:Electron Spin Resonance Spectroscopy; D005296:Ferrous Compounds / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D010833:Phytic Acid / Q000494:pharmacology; D011487:Protein Conformation; D013053:Spectrophotometry; D013057:Spectrum Analysis
D004163:Diphosphoglyceric Acids; D005296:Ferrous Compounds; D006454:Hemoglobins; D019794:2,3-Diphosphoglycerate; D009569:Nitric Oxide; D002995:Clofibric Acid; D010833:Phytic Acid; D001629:Bezafibrate