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Reaction of nitric oxide with heme proteins: studies on metmyoglobin, opossum methemoglobin, and microperoxidase.

Sharma VS, Isaacson RA, John ME, Waterman MR, Chevion M
Biochemistry. 1983 22 (16): 3897-902

PMID: 6311256 · DOI:10.1021/bi00285a026

Kinetic and EPR studies show that the first step in the reaction of NO with ferric myoglobin, opossum hemoglobin, and microperoxidase is the reversible formation of the H-NO complex: H + NO in equilibrium H-NO (where H = Mb+, or Hb+ OP, or MP+). The NO-combination rates are markedly affected by the presence or absence of the distal histidine. The distal histidine significantly reduces the NO-combination rates, perhaps by interaction between the distal histidine and the ferric iron. Thus the beta-chains of Hb+ OP and metmyoglobin show similar combination rates. In the absence of a distal histidine, the NO-combination rates in the alpha-chains of Hb+ OP are much faster and similar to those observed for the five-coordinate heme in microperoxidase. The loss of a water molecule from the six-coordination site is assumed to be the rate-limiting step.

MeSH Terms (10)

Animals Electron Spin Resonance Spectroscopy Hemeproteins Kinetics Methemoglobin Metmyoglobin Nitric Oxide Opossums Peroxidases Spectrophotometry

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