Catalytic action of Mn-superoxide dismutase in scavenging superoxide radical anion by double hydrogen abstraction from dihydrolipoic acid: A theoretical study

2017 ◽  
Vol 117 (11) ◽  
pp. e25355 ◽  
Author(s):  
Ajit Kumar Prasad ◽  
Phool Chand Mishra
Keyword(s):  
Superoxide Dismutase ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Theoretical Study ◽  
Hydrogen Abstraction ◽  
Catalytic Action ◽  
Dihydrolipoic Acid ◽  
Superoxide Radical Anion ◽  
Double Hydrogen

Catalytic role of iron-superoxide dismutase in hydrogen abstraction by super oxide radical anion from ascorbic acid

RSC Advances ◽  
2016 ◽  
Vol 6 (89) ◽  
pp. 86650-86662 ◽  
Author(s):  
Manish K. Tiwari ◽  
Phool C. Mishra
Keyword(s):  
Ascorbic Acid ◽  
Superoxide Dismutase ◽  
Active Site ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Hydrogen Abstraction ◽  
Iron Superoxide Dismutase ◽  
Superoxide Radical Anion ◽  
Catalytic Role

The catalytic role of iron-superoxide dismutase (Fe-SOD) in the working of ascorbic acid (AA) as a superoxide radical anion scavenger has been studied by employing a model developed recently for the active site of the enzyme.

scholarly journals Oxidative denitrification of Nω-hydroxy-l-arginine by the superoxide radical anion

1996 ◽  
Vol 317 (1) ◽  
pp. 17-21 ◽  
Author(s):  
Steven A. EVERETT ◽  
Madeleine F. DENNIS ◽  
Kantilal B. PATEL ◽  
Michael R. L. STRATFORD ◽  
Peter WARDMAN
Keyword(s):  
Nitric Oxide ◽  
Superoxide Dismutase ◽  
Catalytic Activity ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Superoxide Radical Anion ◽  
Prototropic Equilibrium ◽  
Ph Dependent ◽  
Oxide Synthase ◽  
Cytochrome P 450

The superoxide radical anion (O2-•) produced during the catalytic activity of nitric oxide synthase (NOS) and cytochrome P-450 has been implicated in the oxidative denitrification of hydroxyguanidines (> C = NOH). The reactivity of the radiolytically generated O2-• radical with Nω-hydroxy-l-arginine (NHA) is pH dependent and appears to parallel the prototropic equilibrium of the hydroxyguanidino group (> C = NOH ⇌ > C = NO- + H+; pK = 8). The Nω-hydroxyguanidino group is more reactive towards O2-• when deprotonated but exhibits negligible reactivity when protonated. Based on a model, the rate constant for the reaction of the O2-• with NHA was estimated as k (O2-•+ > C = NO-) ≈ 200–500 M-1·s-1, which is probably too low to compete with O2-• reactions with NO• or superoxide dismutase, which occur many orders of magnitude faster. The oxidative elimination of NO from NHA by O2-• was not accompanied by the formation of l-citrulline. Since only 21% of NHA will exist in the deprotonated > C = NO- form at physiological pH, it is unlikely that oxidative denitrification of NHA by cytochrome P-450 or NOS-derived O2-• radicals will prove a major free-radical pathway to NO• and l-citrulline.

scholarly journals Theoretical Study of the Iron Complexes with Aminoguanidine: Investigating Secondary Antioxidant Activity

Antioxidants ◽  
2020 ◽  
Vol 9 (8) ◽  
pp. 756
Author(s):  
Guillermo García-Díez ◽  
Nelaine Mora-Diez
Keyword(s):  
Antioxidant Activity ◽  
Rate Constant ◽  
Thermodynamic Stability ◽  
Radical Anion ◽  
Superoxide Radical ◽  
Theoretical Study ◽  
Initial Step ◽  
Stable Complex ◽  
Oh Radicals ◽  
Superoxide Radical Anion

A thorough analysis of the thermodynamic stability of various complexes of aminoguanidine (AG) with Fe(III) at a physiological pH is presented. Moreover, the secondary antioxidant activity of AG is studied with respect to its kinetic role in the Fe(III) reduction to Fe(II) when reacting with the superoxide radical anion or ascorbate. Calculations are performed at the M05(SMD)/6-311+G(d,p) level of theory. Solvent effects (water) are taken into account in both geometry optimizations and frequency calculations employing the SMD solvation method. Even though the results of this study show that AG can form an extensive number of stable complexes with Fe(III), none of these can reduce the rate constant of the initial step of the Haber–Weiss cycle when the reducing agent is O2•−. However, when the reductant is the ascorbate anion, AG is capable of reducing the rate constant of this reaction significantly, to the point of inhibiting the production of •OH radicals. In fact, the most stable complex of Fe(III) with AG, having a ∆Gf° of −37.9 kcal/mol, can reduce the rate constant of this reaction by 7.9 × 105 times. Thus, AG possesses secondary antioxidant activity relative to the Fe(III)/Fe(II) reduction with ascorbate, but not with O2•−. Similar results have also been found for AG relative to the Cu(II)/Cu(I) reduction, in agreement with experimental results.

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