The oxidation of methionine-54 of epoetinum alfa does not affect molecular structure or stability, but does decrease biological activity

Erythropoietin therapy is used to treat severe anemia in renal failure and chemotherapy patients. One of these therapies based on recombinant human erythropoietin is marketed under the trade name of EPREX and utilizes epoetinum alfa as the active pharmaceutical ingredient. The effect of oxidation of...

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Bibliographic Details
Published inPDA journal of pharmaceutical science and technology Vol. 62; no. 3; p. 211
Main Authors Labrenz, Steven R, Calmann, Melissa A, Heavner, George A, Tolman, Glen
Format Journal Article
LanguageEnglish
Published United States 01.05.2008
Subjects
Allosteric Regulation
Cell Line
Circular Dichroism
Drug Stability
Epoetin Alfa
Erythropoietin - chemistry
Hematinics - chemistry
Hydrogen Peroxide - chemistry
Methionine - analogs & derivatives
Methionine - chemistry
Oxidation-Reduction
Protein Binding
Protein Folding
Recombinant Proteins
Temperature
tert-Butylhydroperoxide - chemistry
Thermodynamics
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Summary:Erythropoietin therapy is used to treat severe anemia in renal failure and chemotherapy patients. One of these therapies based on recombinant human erythropoietin is marketed under the trade name of EPREX and utilizes epoetinum alfa as the active pharmaceutical ingredient. The effect of oxidation of methionine-54 on the structure and stability of the erythropoietin molecule has not been directly tested. We have observed partial and full chemical oxidation of methionine-54 to methionine-54 sulfoxide, accomplished using tert-Butylhydroperoxide and hydrogen peroxide, respectively. A blue shift in the fluorescence center of spectral mass wavelength was observed as a linear response to the level of methionine sulfoxide in the epoetinum alfa molecule, presumably arising from a local change in the environment near tryptophan-51, as supported by potassium iodide quenching studies. Circular dichroism studies demonstrated no change in the folded structure of the molecule with methionine oxidation. The thermal unfolding profiles of partial and completely oxidized epoetinum alfa overlap, with a T(m) of 49.5 degrees C across all levels of methionine sulfoxide content. When the protein was tested for activity, a decrease in biological activity was observed, correlating with methionine sulfoxide levels. An allosteric effect between Met54, Trp51, and residues involved in receptor binding is proposed. These results indicate that methionine oxidation has no effect on the folded structure and global thermodynamic stability of the recombinant human erythropoietin molecule. Oxidation can affect potency, but only at levels significantly in excess of those seen in EPREX.
ISSN:1079-7440