Fig 7. sp6 is an up to 100-fold better IDE-substrate than insulin.
(A) 10 ng of sp6BY or insulin-FITC were incubated with indicated amounts of rIDE for 30 min at 37°C. Remaining amounts of sp6BY and insulin-FITC were detected by measurement of fluorescence excitation. (B) Results of four independently performed experiments. Values represent the arithmetic mean ± SD. (C) Increasing concentrations of sp6BY were incubated with rIDE for 10 min at 37°C. The velocities were calculated from the degradation of sp6BY and normalized for the amount of rIDE. Data points represent values from three independent experiments in a double-reciprocal Lineweaver-Burk plot. The inset shows a magnification of the intersections of the regression lines with the axes. (D) Comparison of KM and vmax values for sp6BY and IDE as determined in (C) to those of IDE and insulin or Aβ as reported [47].