Electron paramagnetic resonance studies of the coordination schemes and site selectivities for divalent metal ions in complexes with pyruvate kinase

Biochemistry ◽  
1990 ◽  
Vol 29 (7) ◽  
pp. 1799-1806 ◽  
Author(s):  
Jenny L. Buchbinder ◽  
George H. Reed
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Metal Ions ◽  
Pyruvate Kinase ◽  
Divalent Metal ◽  
Divalent Metal Ions ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Electron Paramagnetic Resonance as a Probe for Metal Ions and Radicals in Paper

2015 ◽  
Vol 36 (4) ◽  
Author(s):  
Alfonso Zoleo ◽  
Laura Speri ◽  
Maddalena Bronzato
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Metal Ions ◽  
Chemical Species ◽  
Paramagnetic Species ◽  
Paramagnetic Resonance ◽  
Relevant Role ◽  
Historic Paper ◽  
Electron Paramagnetic ◽  
Identification And Characterization

AbstractElectron Paramagnetic Resonance (EPR) is a technique devoted to the identification and characterization of paramagnetic species, i.e. chemical species with unpaired electrons. Very common paramagnetic species which can be detected through EPR in historic paper are Fe(III), Mn(II), Cu(II) ions and radicals, where Fe(III), Cu(II) and radicals play a relevant role in paper degradation. Specifically, Fe(III) is almost ubiquitous in historic paper. Here we propose an overview of the EPR signals in historic and artificially aged paper, and in particular, we would like to show how a deep analysis of EPR signals from paper could provide useful information about the paper’s origin and unique indications of the degradation and oxidation level of the paper.

pH-Dependent amino acid induced conformational changes of rabbit muscle pyruvate kinase

1980 ◽  
Vol 58 (3) ◽  
pp. 188-193 ◽  
Author(s):  
Chiu-Yin Kwan ◽  
Robert C. Davis
Keyword(s):  
Metal Ions ◽  
Pyruvate Kinase ◽  
Conformational Changes ◽  
Divalent Metal ◽  
Rabbit Muscle ◽  
Divalent Metal Ions ◽  
Spectral Changes ◽  
Metal Derivatives ◽  
Muscle Pyruvate Kinase ◽  
Difference Absorption

The interactions of L-Phe and L-Ala with rabbit muscle pyruvate kinase depended upon the nature of divalent metal ions studied: Mg(II), Co(II), Mn(II), and Ni(II). L-Phe inhibited all metal derivatives of the enzyme except Mn(II)–enzyme. L-Ala inhibited only Ni(II)–enzyme and had no effect on other metal derivatives. The inhibition by L-Phe could be partially or completely reversed by L-Ala for all metal derivatives. The mode of inhibition of pyruvate kinase by L-Phe depended upon pH as well as the nature of activating divalent metal ions. The sigmoidal response increased with increasing pH for all metal derivatives inhibited by L-Phe. L-Phe and L-Ala strongly perturbed the coordination sphere of enzyme bound Co(II), but not Ni(II). There were poor correlations between visible circular dichroic (cd) spectral changes and the corresponding kinetic changes. However, L-Phe and (or) L-Ala induced ultraviolet cd and difference absorption spectral changes, on the other hand, corresponded remarkably well with the kinetic observations.

L-Phenylalanine induced changes of sulfhydryl reactivity in rabbit muscle pyruvate kinase

1981 ◽  
Vol 59 (2) ◽  
pp. 92-99 ◽  
Author(s):  
Chiu-Yin Kwan ◽  
Robert C. Davis
Keyword(s):  
Metal Ions ◽  
Pyruvate Kinase ◽  
Divalent Metal ◽  
Enzyme Inactivation ◽  
Rabbit Muscle ◽  
Divalent Metal Ions ◽  
Substrate Analogue ◽  
Metal Derivatives ◽  
Sulfhydryl Modification ◽  
Muscle Pyruvate Kinase

Reactivity of sulfhydryl groups in rabbit muscle pyruvate kinase toward 5,5′-dithiobis(2-nitrobenzoic acid) (DTNB) was studied in the presence of activating divalent metal ions, substrate, substrate analogue, and the allosteric inhibitor, L-Phe. The pattern of sulfhydryl modification in various complexes of pyruvate kinase was consistent with the extent of enzyme inactivation by DTNB under very similar conditions. The sulfhydryl reactivity of Mg(II)-, Co(II)-, and Mn(II)-substituted pyruvate kinase toward DTNB depended upon the nature of the activating divalent metal ions used in the following order of increasing potency, Mg(II) < Mn(II) < Co(II), which is inversely related to the order of catalytic efficiency of these metal ions at alkaline pH. Similar optical spectra and the patterns of sulfhydryl modification by DTNB of the metal derivatives of pyruvate kinase were observed upon the binding of the substrate, phosphoenolpyruvate (PEP), or the substrate analogue, phosphoglycolate, which also provided a complete protection against enzyme inactivation by DTNB. L-Phe, on the other hand, deprotected the enzyme from inactivation and further sulfhydryl modification by DTNB in the presence of PEP with the following order of potency depending upon the activating metal ions, Mn(II) < Co(II) < Mg(II), which parallels the order of metal dependency of L-Phe inhibition of this enzyme. L-Ala, which reverses the L-Phe inhibition of Mg(II)- or Co(II)-activated enzyme, restored the protective effect of PEP in the presence of L-Phe. The different patterns of sulfhydryl reactivity toward Mn(II)–enzyme (hyperbolic) and Mg(II)–enzyme (sigmoidal) correspond well with their kinetic patterns in the presence of L-Phe, indicating the presence of different conformational states between these two metal–enzyme complexes. These results led us to conclude that enzyme sulfhydryl reactivity toward DTNB can be used as a valid index for allosteric conformational changes of rabbit muscle pyruvate kinase.

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