Figure 3.

Reductase activity of heat-treated PDI. rPDI and oPDI were incubated at 25°C or 90°C for 10 min. After cooling, PDI samples were incubated with insulin in DTT-containing buffer for 90 min. The reduction and resulting aggregation of insulin was detected by a change in optical density at 650 nm. Data are reported as the averages ± standard deviations of triplicate samples. (A) The 25°C oPDI sample was incubated with insulin in buffer lacking DTT. Insulin incubated in DTT-containing buffer without PDI was used as an additional control. One of three representative experiments is shown. (B) PDI samples were incubated in the absence or presence of the PDI inhibitor Q3R, as indicated.