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HERO ID
831840
Reference Type
Journal Article
Title
Generation of nitric oxide from nitrite by carbonic anhydrase: a possible link between metabolic activity and vasodilation
Author(s)
Aamand, R; Dalsgaard, T; Jensen, FB; Simonsen, U; Roepstorff, A; Fago, A
Year
2009
Is Peer Reviewed?
Yes
Journal
American Journal of Physiology: Heart and Circulatory Physiology
ISSN:
0363-6135
EISSN:
1522-1539
Volume
297
Issue
6
Page Numbers
H2068-H2074
Language
English
PMID
19820197
DOI
10.1152/ajpheart.00525.2009
Web of Science Id
WOS:000272075300015
Abstract
In catalyzing the reversible hydration of CO2 to bicarbonate and protons, the ubiquitous enzyme carbonic anhydrase (CA) plays a crucial role in CO2 transport, in acid-base balance, and in linking local acidosis to O2 unloading from hemoglobin. Considering the structural similarity between bicarbonate and nitrite, we hypothesized that CA uses nitrite as a substrate to produce the potent vasodilator nitric oxide (NO) to increase local blood flow to metabolically active tissues. Here we show that CA readily reacts with nitrite to generate NO, particularly at low pH, and that the NO produced in the reaction induces vasodilation in aortic rings. This reaction occurs under normoxic and hypoxic conditions and in various tissues at physiological levels of CA and nitrite. Furthermore, two specific inhibitors of the CO2 hydration, dorzolamide and acetazolamide, increase the CA-catalyzed production of vasoactive NO from nitrite. This enhancing effect may explain the known vasodilating effects of these drugs and indicates that CO2 and nitrite bind differently to the enzyme active site. Kinetic analyses show a higher reaction rate at high pH, suggesting that anionic nitrite participates more effectively in catalysis. Taken together, our results reveal a novel nitrous anhydrase enzymatic activity of CA that would function to link the in vivo main end products of energy metabolism (CO2/H+) to the generation of vasoactive NO. The CA-mediated NO production may be important to the correlation between blood flow and metabolic activity in tissues, as occurring for instance in active areas of the brain.
Keywords
acetazolamide; dorzolamide; acidosis; neurovascular coupling
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NAAQS
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