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. Author manuscript; available in PMC: 2010 Jun 25.
Published in final edited form as: Biochemistry. 2008 Oct 21;47(46):12047–12056. doi: 10.1021/bi801604x

FIGURE 2.

FIGURE 2

Reduced PDI as a substrate of QSOX. For each cognate and non-cognate PDI/QSOX pairing the oxidation of reduced PDI was evaluated by following the disappearance of CxxC thiols (using 50–200 μM PDI; 200–800 μM –SH groups; see Experimental Procedures) with 100 nM QSOX in 50 mM phosphate buffer, 1 mM EDTA, at pH 7.5 and 25 °C. Catalase (10 nM) was included in these incubations to discharge the hydrogen peroxide generated by QSOX. Aliquots were withdrawn at the indicated times for analysis of thiol content using DTNB (see Experimental Procedures). Open squares: avian QSOX and the indicated thiol titers of human PDI; filled circles: avian QSOX and avian PDI; filled triangles: human PDI and human QSOX. Crosses and checks indicate thiol consumption in an illustrative control reaction in the absence of QSOX using 250 μM of avian and human PDI respectively.