PMID:10922365

Citation	Gardner, PR, Gardner, AM, Martin, LA, Dou, Y, Li, T, Olson, JS, Zhu, H and Riggs, AF (2000) Nitric-oxide dioxygenase activity and function of flavohemoglobins. sensitivity to nitric oxide and carbon monoxide inhibition. J. Biol. Chem. 275:31581-7
Abstract	Widely distributed flavohemoglobins (flavoHbs) function as NO dioxygenases and confer upon cells a resistance to NO toxicity. FlavoHbs from Saccharomyces cerevisiae, Alcaligenes eutrophus, and Escherichia coli share similar spectra, O(2), NO, and CO binding kinetics, and steady-state NO dioxygenation kinetics. Turnover numbers (V(max)) for S. cerevisiae, A. eutrophus, and E. coli flavoHbs are 112, 290, and 365 NO heme(-1) s(-1), respectively, at 37 degrees C with 200 microm O(2). The K(M) values for NO are low and range from 0.1 to 0.25 microm. V(max)/K(M)(NO) ratios of 900-2900 microm(-1) s(-1) indicate an extremely efficient dioxygenation mechanism. Approximate K(M) values for O(2) range from 60 to 90 microm. NO inhibits the dioxygenases at NO:O(2) ratios of > or =1:100 and makes true K(M)(O(2)) values difficult to determine. High and roughly equal second order rate constants for O(2) and NO association with the reduced flavoHbs (17-50 microm(-1) s(-1)) and small NO dissociation rate constants suggest that NO inhibits the dioxygenase reaction by forming inactive flavoHbNO complexes. Carbon monoxide also binds reduced flavoHbs with high affinity and competitively inhibits NO dioxygenases with respect to O(2) (K(I)(CO) = approximately 1 microm). These results suggest that flavoHbs and related hemoglobins evolved as NO detoxifying components of nitrogen metabolism capable of discriminating O(2) from inhibitory NO and CO.
Links	PubMed Online version:10.1074/jbc.M004141200
Keywords	Alcaligenes/enzymology; Alcaligenes/metabolism; Bacterial Proteins/antagonists & inhibitors; Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Carbon Monoxide/metabolism; Carbon Monoxide/pharmacology; Enzyme Inhibitors/pharmacology; Escherichia coli/enzymology; Escherichia coli/metabolism; Flavin-Adenine Dinucleotide/pharmacology; Fungal Proteins/antagonists & inhibitors; Fungal Proteins/chemistry; Fungal Proteins/metabolism; Hemeproteins/antagonists & inhibitors; Hemeproteins/chemistry; Hemeproteins/metabolism; Kinetics; Ligands; Nitric Oxide/metabolism; Nitric Oxide/pharmacology; Oxygen/metabolism; Oxygen/pharmacology; Oxygenases/antagonists & inhibitors; Oxygenases/chemistry; Oxygenases/metabolism; Protein Binding; Saccharomyces cerevisiae/enzymology; Saccharomyces cerevisiae/metabolism; Spectrophotometry
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
CUPNH:HMP		GO:0008941: nitric oxide dioxygenase activity	ECO:0000314:		F		Figure 6 shows the effects of FAD on the NOD activities of flavoHbs. This suggests dissociation and reassociation of bound FAD during enzyme turnover.	complete CACAO 4744
CUPNH:HMP	enables	GO:0008941: nitric oxide dioxygenase activity	ECO:0000314: direct assay evidence used in manual assertion		F		Seeded From UniProt	complete

References

See Help:References for how to manage references in GONUTS.