scholarly journals Analyzing Xanthine Dehydrogenase Iron-Sulfur Clusters Using Electron Paramagnetic Resonance Spectroscopy

2004 ◽  
Author(s):  
R Hodson
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Xanthine Dehydrogenase ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur ◽  
Electron Paramagnetic

Characterization of iron-sulfur clusters in lysine 2,3-aminomutase by electron paramagnetic resonance spectroscopy

Biochemistry ◽  
1992 ◽  
Vol 31 (44) ◽  
pp. 10774-10781 ◽  
Author(s):  
Robert M. Petrovich ◽  
Frank J. Ruzicka ◽  
George H. Reed ◽  
Perry A. Frey
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Resonance Spectroscopy ◽  
Paramagnetic Resonance ◽  
Iron Sulfur Clusters ◽  
Iron Sulfur ◽  
Electron Paramagnetic

scholarly journals Studies by electron-paramagnetic-resonance spectroscopy and stopped-flow spectrophotometry on the mechanism of action of turkey liver xanthine dehydrogenase

1976 ◽  
Vol 153 (2) ◽  
pp. 297-307 ◽  
Author(s):  
M J Barber ◽  
R C Bray ◽  
D J Lowe ◽  
M P Coughlan
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Redox Potential ◽  
Active Sites ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Xanthine Dehydrogenase ◽  
Resonance Spectroscopy ◽  
Stopped Flow ◽  
Paramagnetic Resonance ◽  
Flow Measurements ◽  
Electron Paramagnetic

Studies by e.p.r. (electron-paramagnetic-resonance) spectroscopy and by stopped-flow spectrophotometry on turkey liver xanthine dehydrogenase revealed strong similarities to as well as important differences from the Veillonella alcalescens xanthine dehydrogenase and milk xanthine oxidase. The turkey enzyme is contaminated by up to three non-functional forms, giving molybdenum e.p.r. signals designated Resting I, Resting II and Slow. Slow and to a lesser extent Resting I signals are like those from the Veillonella enzyme, whereas Resting II is very like a resting signal described by K. V. Rajagopolan, P. Handler, G. Palmer & H. Beinert (1968) (J. Biol. Chem. 243, 3784-3796) for aldehyde oxidase. Another non-functional form that gives the Inhibited signal is produced on treatment of the enzyme with formaldehyde. Stopped-flow measurements at 450 nm show that, as for the milk enzyme, reduction by xanthine is rate-limiting in enzyme turnover. The active enzyme gives rise to Very Rapid and Rapid molybdenum(V) e.p.r. signals, as well as to an FADH signal. That these signals are almost indistinguishable from those of the milk enzyme, confirms the similarities between the active sites. There are two types of iron-sulphur centres that give signals like those in the milk enzyme, though with slightly different parameters. Quantitative reduction titration of the functional enzyme with xanthine revealed two important differences between the turkey and the milk enzymes. First, the turkey enzyme FADH/FADH2 system has a redox potential sufficiently low that xanthine is incapable of reducing the flavin completely. This finding presumably explains the very low oxidase activity. Secondly, whereas the Fe/S II chromophore in the milk enzyme has a relatively high redox potential, for the turkey enzyme the value of this potential is lower and similar to that of its Fe/S I chromophore.

scholarly journals Studies by electron-paramagnetic-resonance spectroscopy on the mechanism of action of xanthine dehydrogenase from Veillonella alcalescens

1976 ◽  
Vol 153 (2) ◽  
pp. 287-295 ◽  
Author(s):  
H Dalton ◽  
D J Lowe ◽  
R T Pawlik ◽  
R C Bray
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectroscopy ◽  
Aldehyde Oxidase ◽  
Detailed Comparison ◽  
Xanthine Dehydrogenase ◽  
Resonance Spectroscopy ◽  
Enzyme Complex ◽  
Partial Reduction ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

E.p.r- (electron-paramagnetic-resonance) spectroscopy was used to compare chemical environment and reactivity of molybdenum, flavin and iron-sulphur centres in the enzyme xanthine dehydrogenase from Veillonella alcalescens (Micrococcus lactilyticus) with those of the corresponding centres in milk xanthine oxidase. The dehydrogenase is frequently contaminated with small but variable amounts of a species resistant to oxidation and giving a new molybdenum (V) e.p.r. signal, “Resting I”. There is also a “desulpho” form of the enzyme giving a Slow Mo(V) signal, indistinguishable from that of the milk enzyme. Molybdenum of the active enzyme behaves in a manner analogous to that of the milk enzyme, giving a Rapid Mo(V) signal on partial reduction with substrates or dithionite. Detailed comparison shows that molybdenum in each enzyme must have the same ligand atoms arranged in the same manner. As with the milk enzyme, complex-formation between reduced dehydrogenase and purine substrate molecules, presumably interacting at the normal substrate-binding site, modifies the Rapid signal, confirming that such substrates interact near molybdenum. The dehydrogenase-flavin semiquinone signal is identical with that of the oxidase but, in contrast, there is only one iron-sulphur signal. The latter gives an e.p.r. spectrum similar to that of aldehyde oxidase.

Sign in / Sign up

Export Citation Format

Share Document