Differential inhibition of purified ERp57 and PDI by rabbit anti-ERp57 Ab 1 and Ab 2. (A-C) The activity of ERp57, PDI, or ERp5 in the presence of Ab 1 (Ab1) and Ab 2 (Ab2) at 10 μg/mL or 30 μg/mL, or normal rabbit IgG (nL IgG) at 30 μg/mL. The amount of EGSH (nM) formed from Di-E-GSSG in the presence of enzyme over 120 seconds is shown. Each point is the composite of at least 3 samples (nL IgG, ●; Ab1 10 μg/mL, ▵; Ab1 30 μg/mL, ▴; Ab2 10 μg/mL, □; Ab2 30 μg/mL, ■). Inhibition was not increased with 60 μg/mL of either Ab (not shown). For these curves, the enzyme was added at ∼ 20 seconds.