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Article Myoglobin: a pseudo‐enzymatic scavenger of nitric oxide
Author(s) -
Ascenzi Paolo,
Brunori Maurizio
Publication year - 2001
Publication title -
biochemistry and molecular biology education
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.34
H-Index - 39
eISSN - 1539-3429
pISSN - 1470-8175
DOI - 10.1111/j.1539-3429.2001.tb00116.x
Subject(s) - myoglobin , nitric oxide , scavenger , ferrous , heme , chemistry , biochemistry , nitrate reductase , hemoglobin , nitrite , enzyme , biophysics , hemeprotein , nitrate , biology , radical , organic chemistry
Myoglobin (Mb) is reported in biochemistry and physiology textbooks to act as an O 2 reservoir and to facilitate O 2 diffusion from capillaries to mitochondria, to sustain cellular respiration. Recently, it has been proposed that Mb is an intracellular scavenger of bioactive nitric oxide (NO), regulating its level in the skeletal and cardiac muscle and thereby protecting mitochondrial respiration, which is impaired by NO. This novel function of Mb is based on the rapid and irreversible reaction of ferrous oxygenated Mb (MbO 2 ) with NO yielding ferric oxidized Mb (metMb) and nitrate (NO 3 ). The efficiency of this process, which is postulated to depend on the superoxide (O 2 ) character acquired by O 2 once bound to the heme iron, may be enhanced by intramolecular diffusion of NO trapped momentarily into cavities of the protein matrix. O 2 can also react with ferrous nitrosylated Mb (MbNO), albeit very slowly, leading to metMb and NO 3 . The O 2 ‐dependent NO‐detoxification process may be considered to be pseudo‐enzymatic given that metMb obtained by the primary reaction of MbO 2 with NO is reduced back to ferrous Mb by a specific metMb‐reductase, and can therefore repeat a cycle of NO conversion to harmless nitrate. © 2001 IUBMB. Published by Elsevier Science Ltd. All rights reserved.