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Published on: February 16, 2022
An S-nitrosothiol (SNO) synthase function of hemoglobin that utilizes nitrite as a substrate
Michael Angelo1, David J Singel, Jonathan S Stamler
1Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA.
Red blood cells regulate blood vessel tone via nitric oxide (NO) interactions with hemoglobin (Hb). This study reveals Hb’s intrinsic S-nitrosothiol synthase activity, crucial for NO bioactivity and impaired in hypoxemic diseases.
Area of Science:
- Biochemistry
- Physiology
- Redox Biology
Background:
- Red blood cells (RBCs) modulate vascular tone by regulating nitric oxide (NO) availability.
- Impaired RBC vasodilation in hypoxemia suggests altered NO-RBC interactions.
- Hemoglobin (Hb) NO partitioning between heme and Cysbeta93 thiol influences NO bioactivity.
Purpose of the Study:
- To investigate the mechanism of S-nitrosohemoglobin (SNO-Hb) formation.
- To identify the role of specific NO-liganded Hb micropopulations in SNO-Hb synthesis.
- To explore the physiological relevance of Hb's S-nitrosothiol synthase activity.
Main Methods:
- Utilized nitrite as the NO source to study Hb reactions.
- Employed spectroscopic and chemical analyses to characterize NO-Hb intermediates.
- Investigated the effects of oxygen, carbon monoxide, and nitrite concentrations on SNO-Hb formation.
Main Results:
- Identified a heme-NO (Fe(III)NO) species in the T-state Hb as a precursor to SNO-Hb.
- Demonstrated rapid SNO-Hb formation from physiological nitrite and deoxyhemoglobin.
- Showed efficient SNO-Hb production via deoxygenation/reoxygenation cycling of oxyHb with nitrite.
Conclusions:
- Tetrameric Hb possesses intrinsic S-nitrosothiol synthase activity dependent on NO-Hb micropopulations.
- This Hb activity is crucial for NO bioactivity and vascular tone regulation.
- Dysfunctional SNO-Hb formation may contribute to cardiopulmonary and blood disorders.
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