Laser kinetic spectroscopy studies of the bimolecular oxygenation of alpha- and beta-subunits within the R-state of human hemoglobin.
Bimolecular oxygenation of tri-liganded R-state human hemoglobin (HbA) is described by bi-exponential kinetics with association rate constants k(alpha) = 27.2 +/- 1.3 (micro M*sec)(-1) and k(beta) = 62.9 +/- 1.6 (micro M*sec)(-1). Both the observed processes have been assigned to the bimolecular oxygenation of alpha- and beta-subunits of the native tetrameric protein by molecular oxygen. The quantum yields of photodissociation within the completely oxygenated R-state HbA are gamma(alpha) = 0.0120 +/- 0.0017 and gamma(beta) = 0.044 +/- 0.005 for alpha- and beta-subunits, respectively. The oxygenation reactions of isolated alpha(PCMB)- and beta(PCMB)-hemoglobin chains are described by mono-exponential kinetics with the association rate constants k(alpha) = 44 +/- 2 (micro M*sec)(-1) and k(beta) = 51 +/- 1 (micro M*sec)(-1), respectively. The quantum yields of photodissociation of isolated alpha(PCMB)- and beta(PCMB)-chains (0.056 +/- 0.006 and 0.065 +/- 0.006, respectively) are greater than that observed for appropriate subunits within the R-state of oxygenated HbA.
Lepeshkevich
S V
SV
Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, Minsk 220072, Belarus. lepeshkevich@imaph.bas-net.by
Konovalova
N V
NV
Dzhagarov
B M
BM
D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D007834:Lasers; D010100:Oxygen / Q000378:metabolism*; D010106:Oxygenators; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D013057:Spectrum Analysis / Q000379:methods*
D006454:Hemoglobins; D021122:Protein Subunits; D010100:Oxygen