Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
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Gene/Protein
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Drug
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Target Concepts:
Gene/Protein
Disease
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Enzyme
Compound
Query: EC:1.7.1.4 (
nitrite reductase
)
1,847
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
Deoxygenated hemoglobin (Hb) is a
nitrite reductase
that reduces naturally occurring nitrite to nitric oxide (NO), supplying physiological relevant NO under hypoxic conditions. The
nitrite reductase
activity is modulated by the allosteric equilibrium between the R and T structures of Hb that also determines oxygen affinity. In the present study we investigated
nitrite reductase
activity and O
2
affinity in Hbs from ten different vertebrate species under identical conditions to disclose interspecific variations and allow an extended test for a correlation between the rate constant for nitrite reduction and O
2
affinity. We also tested plastic changes in Hb properties via addition of T-structure-stabilizing organic phosphates (ATP and
GTP
). The decay in deoxyHb during its reaction with nitrite was exponential-like in ectotherms (Atlantic hagfish, carp, crucian carp, brown trout, rainbow trout, cane toad, Indian python and red-eared slider turtle), while it was sigmoid in mammals (harbor porpoise and rabbit). Typically, hypoxia-tolerant species showed a faster reaction than intolerant species. Addition of ATP and
GTP
decreased O
2
affinity and slowed the rate of nitrite reduction in a concentration-dependent manner. The initial second order rate constant of the deoxyHb-mediated nitrite reduction showed a strong curvilinear correlation with oxygen affinity among all ectothermic vertebrates, and the relationship also applied to plastic variations of Hb properties via organic phosphates. The relationship predicts high
nitrite reductase
activity in hypoxic tolerant species with high Hb-O
2
affinity and reveals that the decrease in erythrocyte ATP and/or
GTP
during acclimation to hypoxia in ectotherms increases the erythrocyte NO generating capacity.
...
PMID:Interspecific variation and plasticity in hemoglobin nitrite reductase activity and its correlation with oxygen affinity in vertebrates. 2810 37
