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Kinetics of the inhibition of mitochondrial respiration by NO
Author(s) -
Koivisto Ari,
Matthias Anita,
Bronnikov Gennady,
Nedergaard Jan
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01258-1
Subject(s) - respiration , kinetics , cytochrome c oxidase , chemistry , mitochondrion , biophysics , cytochrome , electron acceptor , respiration rate , cellular respiration , electron transport chain , biochemistry , biology , enzyme , anatomy , physics , quantum mechanics
The kinetics of the inhibition of mitochondrial respiration by NO was examined in isolated mitochondria (here obtained from rat brown adipose tissue). The K i of NO for the inhibition was ∼27 nM; the IC 50 of NO increased in proportion to the square of an increase in O 2 tension. The K m of O 2 for respiration was ∼16 μM; in the presence of NO, the dependence of respiration on O 2 tension had a Hill coefficient of ∼2. The unusual kinetics is probably related to the ability of cytochrome c oxidase to use 2 NO or 1 O 2 as electron acceptor. The interaction between NO and O 2 in the control of respiration could be described by the formula V O2 (O 2 , NO)= V O2 max·([O 2 ] 2 /((16 μM·(1+[NO]/27 nM)) 2 +[O 2 ] 2 )). Thus, the kinetics is such that respiration in the presence of physiological levels of NO is very sensitive to decreasing O 2 tension.