Catalytic mechanism of the manganese-containing superoxide dismutase of Escherichia coli studied by pulse radiolysis

1974 ◽  
Vol 96 (23) ◽  
pp. 7329-7333 ◽  
Author(s):  
Miriam Pick ◽  
Joseph Rabani ◽  
Frederick Yost ◽  
Irwin Fridovich
Keyword(s):  
Escherichia Coli ◽  
Superoxide Dismutase ◽  
Pulse Radiolysis ◽  
Catalytic Mechanism

scholarly journals The involvement of the bridging imidazolate in the catalytic mechanism of action of bovine superoxide dismutase

1977 ◽  
Vol 167 (1) ◽  
pp. 271-274 ◽  
Author(s):  
M E McAdam ◽  
E M Feilden ◽  
F Lavelle ◽  
L Calabrese ◽  
D Cocco ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Nitrogen Atom ◽  
Mechanism Of Action ◽  
Pulse Radiolysis ◽  
Catalytic Mechanism ◽  
Catalytic Reduction ◽  
Rapid Change ◽  
Proton Donor ◽  
Spectral Changes ◽  
Rapid Protonation

The pulse-radiolysis method has been used to study the catalytic mechanism of O2 leads to dismutation by the Co(II)-substituted bovine erythrocuprein (superoxide dismutase, EC 1.15.1.1). Catalysis is accompanied by spectral changes that may be interpreted in terms of rapid protonation and deprotonation of the Cu-facing nitrogen atom of the imidazolate that bridges the Cu(II) and the Co(II) [or Zn(II)] in the oxidized enzyme. This rapid change permits the possibility that the imidazole is a proton donor in the catalytic reduction of O2 leads to.

scholarly journals A pulse-radiolysis study of the catalytic mechanism of the iron-containing superoxide dismutase from Photobacterium leiognathi

1977 ◽  
Vol 161 (1) ◽  
pp. 3-11 ◽  
Author(s):  
F Lavelle ◽  
M E McAdam ◽  
E M Fielden ◽  
P B Roberts ◽  
K Puget ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Rate Constant ◽  
Pulse Radiolysis ◽  
Ferric Iron ◽  
Catalytic Mechanism ◽  
Order Rate Constant ◽  
Sodium Ascorbate ◽  
Paramagnetic Resonance ◽  
Photobacterium Leiognathi ◽  
Ph Range

The mechanism of the enzymic reaction of an iron-containing superoxide dismutase purified from the marine bacterium Photobacterium leiognathi was studied by using pulse radiolysis. Measurements of activity were done with two different preparations of enzyme containing either 1.6 or 1.15 g-atom of iron/mol. In both cases, identical values of the second-order rate constant for reaction between superoxide dismutase and the superoxide ion in the pH range 6.2-9.0 (k=5.5 X 10(8) M-1-S-1 at pH 8.0) were found. As with the bovine erythrocuprein, there was no evidence for substrate saturation. The effects of reducing agents (H2O2, sodium ascorbate or CO2 radicals) on the visible and the electron-paramagnetic-resonance spectra of the superoxide dismutase containing 1.6 g-atom of ferric iron/mol indicate that this enzyme contains two different types of iron. Turnover experiments demonstrate that only that fraction of the ferric iron that is reduced by H2O2 is involved in the catalysis, being alternately oxidized and reduced by O2; both the oxidation and the reduction steps have a rate constant equal to that measured under turnover conditions. These results are interpreted by assuming that the superoxide dismutase isolated from the organism contains 1 g-atom of catalytic iron/mol and a variable amount of non-catalytic iron. This interpretation is discused in relation to the stoicheiometry reported for iron-containing superoxide dismutases prepared from several other organisms.

scholarly journals Crystal Structure of Escherichia coli Agmatinase: Catalytic Mechanism and Residues Relevant for Substrate Specificity

2021 ◽  
Vol 22 (9) ◽  
pp. 4769
Author(s):  
Pablo Maturana ◽  
María S. Orellana ◽  
Sixto M. Herrera ◽  
Ignacio Martínez ◽  
Maximiliano Figueroa ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Active Site ◽  
Catalytic Mechanism ◽  
Conformational Dynamics ◽  
High Specificity ◽  
Arginine Decarboxylase ◽  
Space Groups ◽  
X Ray Crystallography ◽  
High Dynamics ◽  
Dynamics Simulations

Agmatine is the product of the decarboxylation of L-arginine by the enzyme arginine decarboxylase. This amine has been attributed to neurotransmitter functions, anticonvulsant, anti-neurotoxic, and antidepressant in mammals and is a potential therapeutic agent for diseases such as Alzheimer’s, Parkinson’s, and cancer. Agmatinase enzyme hydrolyze agmatine into urea and putrescine, which belong to one of the pathways producing polyamines, essential for cell proliferation. Agmatinase from Escherichia coli (EcAGM) has been widely studied and kinetically characterized, described as highly specific for agmatine. In this study, we analyze the amino acids involved in the high specificity of EcAGM, performing a series of mutations in two loops critical to the active-site entrance. Two structures in different space groups were solved by X-ray crystallography, one at low resolution (3.2 Å), including a guanidine group; and other at high resolution (1.8 Å) which presents urea and agmatine in the active site. These structures made it possible to understand the interface interactions between subunits that allow the hexameric state and postulate a catalytic mechanism according to the Mn2+ and urea/guanidine binding site. Molecular dynamics simulations evaluated the conformational dynamics of EcAGM and residues participating in non-binding interactions. Simulations showed the high dynamics of loops of the active site entrance and evidenced the relevance of Trp68, located in the adjacent subunit, to stabilize the amino group of agmatine by cation-pi interaction. These results allow to have a structural view of the best-kinetic characterized agmatinase in literature up to now.

Modulation of serum cytokine levels by a novel superoxide dismutase mimetic, M40401, in an Escherichia coli model of septic shock: Correlation with preserved circulating catecholamines*

2003 ◽  
Vol 31 (1) ◽  
pp. 237-245 ◽  
Author(s):  
Heather Macarthur ◽  
Daniel M. Couri ◽  
Gerald H. Wilken ◽  
Thomas C. Westfall ◽  
Andrew J. Lechner ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Septic Shock ◽  
Superoxide Dismutase ◽  
Serum Cytokine ◽  
Cytokine Levels
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