Effects of APAO on PDI activity. (A) Schematic of APAO interaction with thiols. (B) Left: following incubation of 75 nM PDIred with 0 (black), 50 (gray), and 100 (gray stripe) μM APAO for 15 min, assays were initiated by BD-SS addition. Fluorescence after 30 sec was plotted for triplicate experiments normalized to the corresponding value in the absence of APAO. Right: multiple turnover assay incubating PDIox with 5 mM GSH and 0 (black), 50 (gray), or 100 (gray stripe) μM APAO. Percent fluorescence was plotted for triplicate experiments 30 s after BD-SS injection as before.