TY - JOUR
T1 - Characterization of the magnitude and mechanism of aldehyde oxidase-mediated nitric oxide production from nitrite
AU - Li, Haitao
AU - Kundu, Tapan Kumar
AU - Zweier, Jay L.
PY - 2009/12/4
Y1 - 2009/12/4
N2 - Aldehyde oxidase (AO) is a cytosolic enzyme with an important role in drug and xenobiotic metabolism. Although AO has structural similarity to bacterial nitrite reductases, it is unknown whether AO-catalyzed nitrite reduction can be an important source of NO. The mechanism, magnitude, and quantitative importance of AO-mediated nitrite reduction in tissues have not been reported. To investigate this pathway and its quantitative importance, EPR spectroscopy, chemiluminescence NO analyzer, and immunoassays of cGMP formation were performed. The kinetics and magnitude of AO-dependent NO formation were characterized. In the presence of typical aldehyde substrates or NADH, AO reduced nitrite to NO. Kinetics of AO-catalyzed nitrite reduction followed Michaelis-Menten kinetics under anaerobic conditions. Under physiological conditions, nitrite levels are far below its measured Km value in the presence of either the flavin site electron donor NADH or molybdenum site aldehyde electron donors. Under aerobic conditions with the FAD site-binding substrate, NADH, AO-mediated NO production was largely maintained, although with aldehyde substrates oxygen-dependent inhibition was seen. Oxygen tension, substrate, and pH levels were important regulators of AO-catalyzed NO generation. From kinetic data, it was determined that during ischemia hepatic, pulmonary, or myocardial AO and nitrite levels were sufficient to result in NO generation comparable to or exceeding maximal production by constitutive NO synthases. Thus, AO-catalyzed nitrite reduction can bean important source of NO generation, and its NO production will be further increased by therapeutic administration of nitrite.
AB - Aldehyde oxidase (AO) is a cytosolic enzyme with an important role in drug and xenobiotic metabolism. Although AO has structural similarity to bacterial nitrite reductases, it is unknown whether AO-catalyzed nitrite reduction can be an important source of NO. The mechanism, magnitude, and quantitative importance of AO-mediated nitrite reduction in tissues have not been reported. To investigate this pathway and its quantitative importance, EPR spectroscopy, chemiluminescence NO analyzer, and immunoassays of cGMP formation were performed. The kinetics and magnitude of AO-dependent NO formation were characterized. In the presence of typical aldehyde substrates or NADH, AO reduced nitrite to NO. Kinetics of AO-catalyzed nitrite reduction followed Michaelis-Menten kinetics under anaerobic conditions. Under physiological conditions, nitrite levels are far below its measured Km value in the presence of either the flavin site electron donor NADH or molybdenum site aldehyde electron donors. Under aerobic conditions with the FAD site-binding substrate, NADH, AO-mediated NO production was largely maintained, although with aldehyde substrates oxygen-dependent inhibition was seen. Oxygen tension, substrate, and pH levels were important regulators of AO-catalyzed NO generation. From kinetic data, it was determined that during ischemia hepatic, pulmonary, or myocardial AO and nitrite levels were sufficient to result in NO generation comparable to or exceeding maximal production by constitutive NO synthases. Thus, AO-catalyzed nitrite reduction can bean important source of NO generation, and its NO production will be further increased by therapeutic administration of nitrite.
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U2 - 10.1074/jbc.M109.019125
DO - 10.1074/jbc.M109.019125
M3 - Article
C2 - 19801639
AN - SCOPUS:71749090061
SN - 0021-9258
VL - 284
SP - 33850
EP - 33858
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 49
ER -