| 18975018 |
Houghton EA, Nicholas KM: In vitro reactive oxygen species production by histatins and copper (I,II). J Biol Inorg Chem. 2009 Feb;14(2):243-51. Epub 2008 Oct 31.
The ability of the histidine-rich peptides, histatin-5 (Hst-5) and histatin-8 (Hst-8), to support the generation of reactive oxygen species during the Cu-catalyzed oxidation of ascorbate and cysteine has been evaluated. High levels of hydrogen peroxide (70-580 mol/mol Cu/h) are produced by aqueous solutions containing Cu (II), Hst-8 or Hst-5, and a reductant, either ascorbate or cysteine, as determined by the postreaction Amplex Red assay. When the reactions are conducted in the presence of superoxide dismutase, the total hydrogen peroxide produced is decreased, more so in the presence of the peptides (up to 50%), suggesting the intermediacy of superoxide in these reactions. On the other hand, the presence of sodium azide or sodium formate, traps for hydroxyl radicals, has no appreciable effect on the total hydrogen peroxide production for the Cu-Hst systems. EPR spin-trapping studies using 5-(2,2-dimethyl-1,3-propoxy cyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO) in the cysteine-Cu (II) reactions reveal the formation of the CYPMPO-hydroperoxyl and CYPMPO-hydroxyl radical adducts in the presence of Hst-8, whereas only the latter was observed with Cu alone. |
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