Ferric nitrosylated myoglobin catalyzes peroxynitrite scavenging

• Published in: Journal of biological inorganic chemistry 2020-05, Vol.25 (3), p.361-370
• Main Authors: Ascenzi, Paolo, De Simone, Giovanna, Tundo, Grazia R., Platas-Iglesias, Carlos, Coletta, Massimiliano
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Biomedical and Life Sciences; Catalysis; Detoxification; Ferric Compounds - chemistry; Free Radical Scavengers - chemistry; Heme; Inorganic chemistry; Isomerization; Life Sciences; Male; Microbiology; Mitochondria; Molecular Structure; Myoglobin - chemistry; Myoglobins; Nitro Compounds - chemistry; Original Paper; Oxygen; Peroxynitrite; Peroxynitrous Acid - chemistry; Sarcolemma; Whales
• ISSN: 0949-8257; 1432-1327
• DOI: 10.1007/s00775-020-01767-2

Myoglobin (Mb), generally taken as the molecular model of monomeric globular heme-proteins, is devoted: (i) to act as an intracellular oxygen reservoir, (ii) to transport oxygen from the sarcolemma to the mitochondria of vertebrate heart and red muscle cells, and (iii) to act as a scavenger of nitrogen and oxygen reactive species protecting mitochondrial respiration. Here, the first evidence of · NO inhibition of ferric Mb- (Mb(III)) mediated detoxification of peroxynitrite is reported, at pH 7.2 and 20.0 °C. · NO binds to Mb(III) with a simple equilibrium; the value of the second-order rate constant for Mb(III) nitrosylation (i.e., ·NO k on ) is (6.8 ± 0.7) × 10 4  M −1  s −1 and the value of the first-order rate constant for Mb(III)-NO denitrosylation (i.e . , ·NO k off ) is 3.1 ± 0.3 s −1 . The calculated value of the dissociation equilibrium constant for Mb(III)-NO complex formation (i.e., ·NO k off / ·NO k on  = (4.6 ± 0.7) × 10 −5  M) is virtually the same as that directly measured (i.e., ·NO K  = (3.8 ± 0.5) × 10 −5  M). In the absence of · NO, Mb(III) catalyzes the conversion of peroxynitrite to NO 3 − , the value of the second-order rate constant (i.e . , P k on ) being (1.9 ± 0.2) × 10 4  M −1  s −1 . However, in the presence of · NO, Mb(III)-mediated detoxification of peroxynitrite is only partially inhibited, underlying the possibility that also Mb(III)-NO is able to catalyze the peroxynitrite isomerization, though with a reduced rate ( P k on * = (2.8 ± 0.3) × 10 3  M −1  s −1 ). These data expand the multiple roles of · NO in modulating heme-protein actions, envisaging a delicate balancing between peroxynitrite and · NO, which is modulated through the relative amount of Mb(III) and Mb(III)-NO. Graphic abstract