Abstract
Catalysis of hydrogen peroxide dismutation by the dimanganese catalase from Thermus thermophilus has been measured and found to obey Michaelis-Menton kinetics with no evidence for substrate inhibition at concentrations up to 0.45 M H2O2. Comparison among three dimanganese catalases (Thermus thermophilus. Thermoleophilium album, and Lactobacillus plantarum) reveals that their apparent second-order rate constants, kcat/Km, differ by at most a factor of 5, even though the individual kinetic constants differ by as much as a factor of 20. This similarity suggests that all three enzymes may have the same rate-determining step. For T. thermophilus catalase we find that kcat/Km ∼ kbi, the bimolecular rate constant at limiting substrate concentrations. Thus, the rate of the rate-determining step is unaltered over the entire range of substrate concentrations, unlike T. album and L. plantarum catalases where substrate inhibition has been reported. Comparison to structurally characterized dimanganese complexes and dimetalloproteins (arginase, hemerythrin), which are functional, albeit kinetically slow, catalase mimics, reveals that high catalase activity correlates with a greater number of stronger σ-ligand donors like anionic carboxylatos vs neutral histidines that stabilize the oxidized Mn2(III,III) state over reduced Mn2(II,II). A critical feature for enzymatic functionality in vivo is suppression of one-electron chemistry leading to formation of the mixed-valence forms, Mn2(III,IV) and Mn2(II,III), which are kinetically inactive or precursors to inactive species, respectively. Evidence is presented from model compounds suggesting that the μ-carboxylato bridge between Mn ions in catalase may play the key role in suppressing formation of these detrimental oxidation states through destabilization of these one-electron redox processes.
| Original language | English |
|---|---|
| Pages (from-to) | 15433-15436 |
| Number of pages | 4 |
| Journal | Biochemistry |
| Volume | 33 |
| Issue number | 51 |
| Publication status | Published - 1994 |
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Protein coordination to manganese determines the high catalytic rate of dimanganese catalases. Comparison to functional catalase mimics. / Shank, Mary; Barynin, Vladimir; Dismukes, G Charles.
In: Biochemistry, Vol. 33, No. 51, 1994, p. 15433-15436.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Protein coordination to manganese determines the high catalytic rate of dimanganese catalases. Comparison to functional catalase mimics
AU - Shank, Mary
AU - Barynin, Vladimir
AU - Dismukes, G Charles
PY - 1994
Y1 - 1994
N2 - Catalysis of hydrogen peroxide dismutation by the dimanganese catalase from Thermus thermophilus has been measured and found to obey Michaelis-Menton kinetics with no evidence for substrate inhibition at concentrations up to 0.45 M H2O2. Comparison among three dimanganese catalases (Thermus thermophilus. Thermoleophilium album, and Lactobacillus plantarum) reveals that their apparent second-order rate constants, kcat/Km, differ by at most a factor of 5, even though the individual kinetic constants differ by as much as a factor of 20. This similarity suggests that all three enzymes may have the same rate-determining step. For T. thermophilus catalase we find that kcat/Km ∼ kbi, the bimolecular rate constant at limiting substrate concentrations. Thus, the rate of the rate-determining step is unaltered over the entire range of substrate concentrations, unlike T. album and L. plantarum catalases where substrate inhibition has been reported. Comparison to structurally characterized dimanganese complexes and dimetalloproteins (arginase, hemerythrin), which are functional, albeit kinetically slow, catalase mimics, reveals that high catalase activity correlates with a greater number of stronger σ-ligand donors like anionic carboxylatos vs neutral histidines that stabilize the oxidized Mn2(III,III) state over reduced Mn2(II,II). A critical feature for enzymatic functionality in vivo is suppression of one-electron chemistry leading to formation of the mixed-valence forms, Mn2(III,IV) and Mn2(II,III), which are kinetically inactive or precursors to inactive species, respectively. Evidence is presented from model compounds suggesting that the μ-carboxylato bridge between Mn ions in catalase may play the key role in suppressing formation of these detrimental oxidation states through destabilization of these one-electron redox processes.
AB - Catalysis of hydrogen peroxide dismutation by the dimanganese catalase from Thermus thermophilus has been measured and found to obey Michaelis-Menton kinetics with no evidence for substrate inhibition at concentrations up to 0.45 M H2O2. Comparison among three dimanganese catalases (Thermus thermophilus. Thermoleophilium album, and Lactobacillus plantarum) reveals that their apparent second-order rate constants, kcat/Km, differ by at most a factor of 5, even though the individual kinetic constants differ by as much as a factor of 20. This similarity suggests that all three enzymes may have the same rate-determining step. For T. thermophilus catalase we find that kcat/Km ∼ kbi, the bimolecular rate constant at limiting substrate concentrations. Thus, the rate of the rate-determining step is unaltered over the entire range of substrate concentrations, unlike T. album and L. plantarum catalases where substrate inhibition has been reported. Comparison to structurally characterized dimanganese complexes and dimetalloproteins (arginase, hemerythrin), which are functional, albeit kinetically slow, catalase mimics, reveals that high catalase activity correlates with a greater number of stronger σ-ligand donors like anionic carboxylatos vs neutral histidines that stabilize the oxidized Mn2(III,III) state over reduced Mn2(II,II). A critical feature for enzymatic functionality in vivo is suppression of one-electron chemistry leading to formation of the mixed-valence forms, Mn2(III,IV) and Mn2(II,III), which are kinetically inactive or precursors to inactive species, respectively. Evidence is presented from model compounds suggesting that the μ-carboxylato bridge between Mn ions in catalase may play the key role in suppressing formation of these detrimental oxidation states through destabilization of these one-electron redox processes.
UR - http://www.scopus.com/inward/record.url?scp=0028574375&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0028574375&partnerID=8YFLogxK
M3 - Article
C2 - 7803407
AN - SCOPUS:0028574375
VL - 33
SP - 15433
EP - 15436
JO - Biochemistry
JF - Biochemistry
SN - 0006-2960
IS - 51
ER -