The DOI matches its Crossref record; 57 of the 57 references it cites were found in a registry or an index.
Enzymatic function of hemoglobin as a nitrite reductase that produces NO under allosteric control
Open accessAbstract
Hypoxic vasodilation is a fundamental, highly conserved physiological response that requires oxygen and/or pH sensing coupled to vasodilation. While this process was first characterized more than 80 years ago, the precise identity and mechanism of the oxygen sensor and mediators of vasodilation remain uncertain. In support of a possible role for hemoglobin (Hb) as a sensor and effector of hypoxic vasodilation, here we show biochemical evidence that Hb exhibits enzymatic behavior as a nitrite reductase, with maximal NO generation rates occurring near the oxy-to-deoxy (R-to-T) allosteric structural transition of the protein. The observed rate of nitrite reduction by Hb deviates from second-order kinetics, and sigmoidal reaction progress is determined by a balance between 2 opposing chemistries of the heme in the R (oxygenated conformation) and T (deoxygenated conformation) allosteric quaternary structures of the Hb tetramer--the greater reductive potential of deoxyheme in the R state tetramer and the number of unligated deoxyheme sites necessary for nitrite binding, which are more plentiful in the T state tetramer. These opposing chemistries result in a maximal nitrite reduction rate when Hb is 40-60% saturated with oxygen (near the Hb P50), an apparent ideal set point for hypoxia-responsive NO generation. These data suggest that the oxygen sensor for hypoxic vasodilation is determined by Hb oxygen saturation and quaternary structure and that the nitrite reductase activity of Hb generates NO gas under allosteric and pH control.
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In the citing paper
“They showed that nitrite bioactivation is most prevalent during rapid deoxygenation, reaching a maximum conversion and nitric oxide-mediated effects at 50% oxygen bound hemoglobin.73,74”
From Nitrate-Nitrite-Nitric Oxide Pathway: Implications for Anesthesiology and Intensive Care (2010) · cites this paper as [73]
Experimental — accuracy not yet measuredThe source backs part of the claim, not all of it — or backs it for a different population, condition or comparison.
In the citing paper
“Nitrite appears to mediate the majority of its effects through bioactivation to NO.This occurs mainly via nitrite reductases, which have selective activity under oxygen/hypoxic/ischaemic conditions”
From Vascular effects of dietary nitrate (as found in green leafy vegetables and beetroot) via the nitrate-nitrite-nitric oxide pathway (2013) · cites this paper as [120]
Experimental — accuracy not yet measuredIn the citing paper
“The reaction of deoxyHb with nitrite shows an increase in the instantaneous reaction rate as the reaction progresses (447). Studies with T-state and R-state Hb–stabilizing compounds have unambiguously identified the reason for this change is the shift from T-state to R-state during the course of the reaction, as the NO formed in the reaction binds to the unreacted deoxyHb to stabilize the R-state.”
From Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation (2019) · cites this paper as [447]
In the citing paper
“The rate constants for the reaction of Hb with nitrite change from 0.12 M−1s−1 for T-state Hb to 6.0 M−1s−1 for R-state Hb (Table 3) (447).”
From Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation (2019) · cites this paper as [447]
In the citing paper
“This scheme has been found to apply to virtually all the heme protein–mediated nitrite reduction reactions studied to date, including Hb (248, 447), Mb (247, 862), neuroglobin (Ngb) (932, 945), Cygb (182, 571, 780), cystathionine β-synthase (CBS) (149, 350), globin X (184), plant and cyanobacterial Hb (phytohemoglobins) (905, 946), flavohemoglobin (340), heme-albumin (43), cytochrome c (41), prot”
From Sources of Vascular Nitric Oxide and Reactive Oxygen Species and Their Regulation (2019) · cites this paper as [447]
In the citing paper
“Nitrite metabolism can be activated by hypoxia, low pH and reactions with metalloproteins[50–58].”
From Enterosalivary nitrate metabolism and the microbiome: Intersection of microbial metabolism, nitric oxide and diet in cardiac and pulmonary vascular health (2017) · cites this paper as [53]
In the citing paper
“As with NOS-derived NO, inorganic nitrite demonstrates robust NO-signaling effects[52,53,57,59] and contributes to basal vascular tone[51,55,60,61], blood pressure[62–66], protection from endothelial dysfunction[67–71] and vascular inflammation[72] under conditions of metabolic and inflammatory stress.”
From Enterosalivary nitrate metabolism and the microbiome: Intersection of microbial metabolism, nitric oxide and diet in cardiac and pulmonary vascular health (2017) · cites this paper as [53]
In the citing paper
“(1)NO2−+HbFe2++H+→NO+HbFe3++OH−”
From Mechanisms of nitrite bioactivation (2014) · cites this paper as [36]
In the citing paper
“Interestingly, the rate of reduction has been found to depend on the allosteric state of the protein, with vacant hemes in an R-state Hb tetramer reacting about 100 times faster than those in the T-state [36–38].”
From Mechanisms of nitrite bioactivation (2014) · cites this paper as [36]
In the citing paper
“The rate of NO production is thus maximal at partial oxygen saturations near the p50 of Hb (Figure 3) [36, 38].”
From Mechanisms of nitrite bioactivation (2014) · cites this paper as [36]
In the citing paper
“The maximum rate of NO production at this oxygen pressure, taking a bimolecular rate constant of 1 M−1s−1 [36], 0.01 M heme, and 100 nM nitrite would be 1 nanomolar/sec.”
From Mechanisms of nitrite bioactivation (2014) · cites this paper as [36]
In the citing paper
“This differential reactivity of nitrite reduction versus oxidation being controlled by oxygen tension (i.e. presence of deoxygenated vs oxygenated hemoglobin / myoglobin) illustrates the biochemical mechanism underlying the proposed model in which nitrite can selectively produce NO during graded hypoxia [5, 25-28].”
From Current perspectives and challenges in understanding the role of nitrite as an integral player in nitric oxide biology and therapy (2011) · cites this paper as [27]
In the citing paper
“However, experiments by Cosby et al showed that intra-arterial infusion of nitrite at near-physiological levels causes vasodilation in an arterio-venous gradient manner that is influenced by R-T state conversion and oxygen tension implicating red cell reduction of nitrite to NO [19, 106, 107].”
From Inorganic nitrite therapy: historical perspective and future directions (2011) · cites this paper as [107]
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Metadata
- Authors
- Huang, Z.
- Affiliations
- National Institutes of Health (US)
- Corresponding author
- Huang, Z.
- ORCID
- Huang, Z.
- Venue
- Journal of Clinical Investigation
- Published
- 2005-08-01
- Volume
- 115
- Issue
- 8
- Pages
- 2099-2107
- ISSN
- 0021-9738 (ISSN-L)
- PMC
- PMC1177999
- OpenAlex
- W2120714892
- Cited by
- 520
- References
- 57
- Citations by year
- 2026: 7 · 2025: 6 · 2024: 16 · 2023: 18 · 2022: 9 · 2021: 11 · 2020: 17 · 2019: 19 · 2018: 21 · 2017: 20 · 2016: 25 · 2015: 29 · 2014: 33 · 2013: 41 · 2012: 40
- FWCI
- 13.83
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Clinical Investigation (publishedVersion)
- Europe PMC (PubMed Central) (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Funders
- North Carolina Biotechnology Center
- National Institutes of Health (GM55792, HL58091)
- National Heart, Lung, and Blood Institute (R29HL058091, R37HL058091, HL58091, R01HL058091)
- National Institute of General Medical Sciences (R29GM055792, GM55792, R01GM055792)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Biochemistry › Hemoglobin structure and function
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heme Oxygenase-1 and Carbon Monoxide
- Health Sciences › Medicine › Physiology (medical) › Nitric Oxide and Endothelin Effects
- Keywords
- hemoglobin, nitrite reductase, nitric oxide production, hypoxic vasodilation, oxygen sensing, allosteric transition, pH control, oxygen saturation
- MeSH terms
- Allosteric Regulation, Allosteric Site, Animals, Hypoxia, Hemoglobins, Horses, Humans, Hydrogen-Ion Concentration, Kinetics, Nitric Oxide, Nitrite Reductases, Nitrites, Oxidation-Reduction, Vasodilation, Protein Structure, Tertiary
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