Figure 5.

The C domain can reduce the disulfides of insulin. The activity was measured with 20 μM of the enzyme indicated on the graph. The thioredoxin is from E. coli. The activity of the R domain and APR1p was not greater than the spontaneous rate in a reaction lacking protein. The assay measures the precipitation of the insulin β chain, detected as an increase in turbidity at 650 nm. A reaction with 20 μM glutaredoxin (Grx1) gave a curve that lies between the curves of thioredoxin and C domain (not shown).