Phenoxyl, (Methylthio)phenoxyl, and (Methylthio)cresyl Radical Models for the Structures, Vibrations, and Spin Properties of the Cysteine-Linked Tyrosyl Radical in Galactose Oxidase

1999 ◽  
Vol 103 (22) ◽  
pp. 4764-4772 ◽  
Author(s):  
Kristopher E. Wise ◽  
J. Brett Pate ◽  
Ralph A. Wheeler
Keyword(s):  
Galactose Oxidase ◽  
Tyrosyl Radical ◽  
Spin Properties

Tyrosyl radical in galactose oxidase not strongly perturbed by cysteine cross-link

1999 ◽  
Vol 313 (1-2) ◽  
pp. 374-378 ◽  
Author(s):  
Fahmi Himo ◽  
Gerald T Babcock ◽  
Leif A Eriksson
Keyword(s):  
Galactose Oxidase ◽  
Tyrosyl Radical ◽  
Cross Link

Mechanistic studies on the single copper tyrosyl-radical containing enzyme galactose oxidase

1998 ◽  
Vol 70 (4) ◽  
pp. 897-902 ◽  
Author(s):  
C. D. Borman ◽  
C. G. Saysell ◽  
C. Wright ◽  
A. G. Sykes
Keyword(s):  
Galactose Oxidase ◽  
Tyrosyl Radical ◽  
Mechanistic Studies

gTensor and Spin Density of the Modified Tyrosyl Radical in Galactose Oxidase:  A Density Functional Study

2003 ◽  
Vol 107 (1) ◽  
pp. 331-337 ◽  
Author(s):  
Martin Kaupp ◽  
Tobias Gress ◽  
Roman Reviakine ◽  
Olga L. Malkina ◽  
Vladimir G. Malkin
Keyword(s):  
Spin Density ◽  
Density Functional ◽  
Galactose Oxidase ◽  
Functional Study ◽  
Tyrosyl Radical ◽  
Density Functional Study

Ab initio g-tensor calculations of the thioether substituted tyrosyl radical in galactose oxidase

2000 ◽  
Vol 319 (3-4) ◽  
pp. 191-196 ◽  
Author(s):  
Maria Engström ◽  
Fahmi Himo ◽  
Hans Ågren
Keyword(s):  
Ab Initio ◽  
Galactose Oxidase ◽  
Tyrosyl Radical

scholarly journals The Stacking Tryptophan of Galactose Oxidase:  A Second-Coordination Sphere Residue that Has Profound Effects on Tyrosyl Radical Behavior and Enzyme Catalysis†,‡

Biochemistry ◽  
2007 ◽  
Vol 46 (15) ◽  
pp. 4606-4618 ◽  
Author(s):  
Melanie S. Rogers ◽  
Ejan M. Tyler ◽  
Nana Akyumani ◽  
Christian R. Kurtis ◽  
R. Kate Spooner ◽  
...  
Keyword(s):  
Coordination Sphere ◽  
Enzyme Catalysis ◽  
Galactose Oxidase ◽  
Tyrosyl Radical ◽  
Second Coordination Sphere

Activation of cytochrome c to a peroxidase compound I-type intermediate by H2O2: relevance to redox signalling in apoptosis

2004 ◽  
Vol 71 ◽  
pp. 97-106 ◽  
Author(s):  
Mark Burkitt ◽  
Clare Jones ◽  
Andrew Lawrence ◽  
Peter Wardman
Keyword(s):  
Cytochrome C ◽  
Hydroxyl Radical ◽  
Redox Regulation ◽  
Chemotherapeutic Agents ◽  
Tyrosyl Radical ◽  
Compound I ◽  
Definitive Evidence ◽  
Enhanced Production ◽  
Physico Chemical

The release of cytochrome c from mitochondria during apoptosis results in the enhanced production of superoxide radicals, which are converted to H2O2 by Mn-superoxide dismutase. We have been concerned with the role of cytochrome c/H2O2 in the induction of oxidative stress during apoptosis. Our initial studies showed that cytochrome c is a potent catalyst of 2′,7′-dichlorofluorescin oxidation, thereby explaining the increased rate of production of the fluorophore 2′,7′-dichlorofluorescein in apoptotic cells. Although it has been speculated that the oxidizing species may be a ferryl-haem intermediate, no definitive evidence for the formation of such a species has been reported. Alternatively, it is possible that the hydroxyl radical may be generated, as seen in the reaction of certain iron chelates with H2O2. By examining the effects of radical scavengers on 2′,7′-dichlorofluorescin oxidation by cytochrome c/H2O2, together with complementary EPR studies, we have demonstrated that the hydroxyl radical is not generated. Our findings point, instead, to the formation of a peroxidase compound I species, with one oxidizing equivalent present as an oxo-ferryl haem intermediate and the other as the tyrosyl radical identified by Barr and colleagues [Barr, Gunther, Deterding, Tomer and Mason (1996) J. Biol. Chem. 271, 15498-15503]. Studies with spin traps indicated that the oxo-ferryl haem is the active oxidant. These findings provide a physico-chemical basis for the redox changes that occur during apoptosis. Excessive changes (possibly catalysed by cytochrome c) may have implications for the redox regulation of cell death, including the sensitivity of tumour cells to chemotherapeutic agents.

Functional Fractionation of Platelets: Aggregation Kinetics and Glycoprotein Labeling of Differing Platelet Populations

1982 ◽  
Vol 48 (02) ◽  
pp. 211-216 ◽  
Author(s):  
V M Haver ◽  
A R L Gear
Keyword(s):  
Galactose Oxidase ◽  
Aggregation Kinetics ◽  
Maximal Rate ◽  
Membrane Glycoproteins ◽  
Whole Cells ◽  
Reversible Aggregation ◽  
Significant Difference ◽  
Small Doses ◽  
Major Loss ◽  
Kinetics Of

SummaryPlatelet heterogeneity has been studied with a technique called functional fractionation which employs gentle centrifugation to yield subpopulations (“reactive” and “less-reactive” platelets) after exposure to small doses of aggregating agent. Aggregation kinetics of the different platelet populations were investigated by quenched-flow aggregometry. The large, “reactive” platelets were more sensitive to ADP (Ka = 1.74 μM) than the smaller “less-reactive” platelets (Ka = 4.08 μM). However, their maximal rate of aggregation (Vmax, % of platelets aggregating per sec) of 23.3 was significantly lower than the “less-reactive” platelets (Vmax = 34.7). The “reactive” platelets had a 2.2 fold higher level of cyclic AMP.Platelet glycoproteins were labeled using the neuraminidase-galactose oxidase – [H3]-NaBH4 technique. When platelets were labeled after reversible aggregation, the “reactive” platelets showed a two-fold decrease in labeling efficiency (versus control platelets). However, examination of whole cells or membrane preparations from reversibly aggregated platelets revealed no significant difference in Coomassie or PAS (Schiff) staining.These results suggest that the large, “reactive” platelets are more sensitive to ADP but are not hyperaggregable in a kinetic sense. Reversible aggregation may cause a re-orientation of membrane glycoproteins that is apparently not characterized by a major loss of glycoprotein material.

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