The mechanism of autooxidation of myoglobin.

Brantley, R E; Smerdon, Stephen J.; Wilkinson, Anthony J.; Singleton, Eileen W.; Olson, John S.

doi:10.1016/s0021-9258(18)53138-0

Cited by 378 publications

(282 citation statements)

References 33 publications

Supporting

Mentioning

261

Contrasting

Unclassified

Order By: Relevance

“…The auto-oxidation mechanism involves the transfer of an electron from the ferrous iron atom to the bound or nearby oxygen (Wallace et a]., 1982;Brantley et a]., 1993;Dickerson et al, 1993;Sugawara et al, 1993;Balagopalakrishna et al, 1996), which produces the superoxide ion: (Fe2+-02) + (Fe3+-H20) + 0,.…”

Section: Auto-oxidationmentioning

confidence: 99%

Tetramer‐dimer equilibrium of oxyhemoglobin mutants determined from auto‐oxidation rates

et al. 1998

View full text Add to dashboard Cite

One of the main difficulties with blood substitutes based on hemoglobin (Hb) solutions is the auto-oxidation of the hemes, a problem aggravated by the dimerization of Hb tetramers. We have employed a method to study the oxyHb tetramer-dimer equilibrium based on the rate of auto-oxidation as a function of protein concentration. The 16-fold difference in dimer and tetramer auto-oxidation rates (in 20 mM phosphate buffer at pH 7.0, 37 "C) was exploited to determine the fraction dimer. The results show a transition of the auto-oxidation rate from low to high protein concentrations, allowing the determination of the tetramer-dimer dissociation coefficient14-fold increase in K4,2 was observed for addition of 10 mM of the allosteric effector inositol hexaphosphate (IHP).Recombinant hemoglobins (rHb) were genetically engineered to obtain Hb with a lower oxygen affinity than native Hb (Hb A). The rHb a 9 2 [(C7) F41Y/(G4) N102Yl shows a fivefold increase in K4.2 at pH 7.0,37"C. An atmosphere of pure oxygen is necessary in this case to insure fully oxygenated Hb. When this condition is satisfied, this method provides an efficient technique to characterize both the tetramer-dimer equilibrium and the auto-oxidation rates of various oxyHb. For low oxygen affhity Hb equilibrated under air, the presence of deoxy subunits accelerates the auto-oxidation. Although a full analysis is complicated, the auto-oxidation studies for air equilibrated samples are more relevant to the development of a blood substitute based on Hb solutions. The double mutants, rHb a2p2 [(C7) F41Y/(G4) N102Al and rHb a2p2 [(C7) F41Y/(E10) K66T], show a lower oxygen afflnity and a higher rate of oxidation than Hb A. Simulations of the auto-oxidation rate versus Hb concentration indicate that very high protein concentrations are required to observe the tetramer auto-oxidation rate. Because the dimers oxidize much more rapidly, even a small fraction dimer will influence the observed oxidation rate.Keywords: auto-oxidation; hemoglobin; oxyhemoglobin; recombinant hemoglobin; tetramer-dimer equilibrium Despite the vast amount of research on hemoglobin (Hb), there are no rapid and reliable methods to measure the fraction of dimers. This is due to the difficulty of obtaining a reliable signal that differenciates between the dimeric and tetrameric species. Dimers have spectral and ligand binding properties similar to fully liganded tetramers. In addition, it is difficult to obtain data for pure dimers at pH 7, because one must use protein concentrations below 100 nM-a condition where the equilibria for the globin-heme (or hemin) and the monomerization may influence the results.

show abstract

Section: Auto-oxidationmentioning

confidence: 99%

Tetramer‐dimer equilibrium of oxyhemoglobin mutants determined from auto‐oxidation rates

et al. 1998

View full text Add to dashboard Cite

show abstract

“…As reported for heme-based sensors [59], the highly solvent-exposed heme-Fe(II) atom [26] of Mt-Nb(II) and Hs-Nb(II) undergoes instantaneous O 2 -mediated oxidation, the auto-oxidation rate being 10 4 -10 5 times larger than that of Pc-Mb(II) [16]. Therefore 10 −4 s (12 %) and τ2 = 0.0071 ± 0.0002 s (88 %).…”

Section: O 2 Dissociation From Mt-nb(ii)-o 2 and Hs-nb(ii)-omentioning

confidence: 66%

Mycobacterial and Human Ferrous Nitrobindins: Spectroscopic and Reactivity Properties

Masi

Pesce

et al. 2021

IJMS

View full text Add to dashboard Cite

Structural and functional properties of ferrous Mycobacterium tuberculosis (Mt-Nb) and human (Hs-Nb) nitrobindins (Nbs) were investigated. At pH 7.0 and 25.0 °C, the unliganded Fe(II) species is penta-coordinated and unlike most other hemoproteins no pH-dependence of its coordination was detected over the pH range between 2.2 and 7.0. Further, despite a very open distal side of the heme pocket (as also indicated by the vanishingly small geminate recombination of CO for both Nbs), which exposes the heme pocket to the bulk solvent, their reactivity toward ligands, such as CO and NO, is significantly slower than in most hemoproteins, envisaging either a proximal barrier for ligand binding and/or crowding of H2O molecules in the distal side of the heme pocket which impairs ligand binding to the heme Fe-atom. On the other hand, liganded species display already at pH 7.0 and 25 °C a severe weakening (in the case of CO) and a cleavage (in the case of NO) of the proximal Fe-His bond, suggesting that the ligand-linked movement of the Fe(II) atom onto the heme plane brings about a marked lengthening of the proximal Fe-imidazole bond, eventually leading to its rupture. This structural evidence is accompanied by a marked enhancement of both ligands dissociation rate constants. As a whole, these data clearly indicate that structural–functional relationships in Nbs strongly differ from what observed in mammalian and truncated hemoproteins, suggesting that Nbs play a functional role clearly distinct from other eukaryotic and prokaryotic hemoproteins.

show abstract

Section: Resultsmentioning

confidence: 99%

“…Autoxidation of ferrous myoglobin to metmyoglobin is strongly influenced by the constitution of the distal pocket [40, 41] . For example, the H64V and V68A mutations, which we introduced to promote carbene chemistry, are known to accelerate this process by factors of 600 and 5, respectively [41] . As a consequence, in contrast to sperm whale oxymyoglobin, MbO 2 , which has a t 1/2 of ≈13 h at pH 7.0, [41] Mb*O 2 autoxidizes with a t 1/2 of a few minutes.…”

Section: Resultsmentioning

confidence: 99%

“…[40,41] Fore xample,t he H64V and V68A mutations,w hich we introduced to promote carbene chemistry,a re known to accelerate this process by factors of 600 and 5, respectively. [41] As aconsequence,incontrast to sperm whale oxymyoglobin, MbO 2 ,w hich has a t 1/2 of % 13 ha tp H7.0, [41] Mb*O 2 autoxidizes with a t 1/2 of af ew minutes.M b*(3ThiA) and Mb*(4Thz) are much more reactive,m aking isolation of the corresponding oxy complexes difficult, whereas the NMH variant reacts somewhat slower (t 1/2 = 12 min). Strikingly, pairing 5Thz with the distal mutations dramatically slows autoxidation, explaining why we were able to crystallize the oxy complex.…”

Section: Uv/vis Spectroscopic Characterizationmentioning

confidence: 99%

See 1 more Smart Citation

Noncanonical Heme Ligands Steer Carbene Transfer Reactivity in an Artificial Metalloenzyme**

et al. 2021

View full text Add to dashboard Cite

Changing the primary metal coordination sphere is a powerful strategy for tuning metalloprotein properties. Here we used amber stop codon suppression with engineered pyrrolysyl‐tRNA synthetases, including two newly evolved enzymes, to replace the proximal histidine in myoglobin with Nδ‐methylhistidine, 5‐thiazoylalanine, 4‐thiazoylalanine and 3‐(3‐thienyl)alanine. In addition to tuning the heme redox potential over a >200 mV range, these noncanonical ligands modulate the protein's carbene transfer activity with ethyl diazoacetate. Variants with increased reduction potential proved superior for cyclopropanation and N–H insertion, whereas variants with reduced Eo values gave higher S–H insertion activity. Given the functional importance of histidine in many enzymes, these genetically encoded analogues could be valuable tools for probing mechanism and enabling new chemistries.

show abstract

The mechanism of autooxidation of myoglobin.

Cited by 378 publications

References 33 publications

Tetramer‐dimer equilibrium of oxyhemoglobin mutants determined from auto‐oxidation rates

Tetramer‐dimer equilibrium of oxyhemoglobin mutants determined from auto‐oxidation rates

Mycobacterial and Human Ferrous Nitrobindins: Spectroscopic and Reactivity Properties

Noncanonical Heme Ligands Steer Carbene Transfer Reactivity in an Artificial Metalloenzyme**

Contact Info

Product

Resources

About