Kinetics of LD78β processing by CD26/DPP IV.

We incubated 5 μg intact synthetic LD78β at 37°C with 0.1 unit pure soluble CD26/DPP IV in 200 μL of 100 mmol/L Tris (pH 8.5); 20 μL samples were taken at the indicated time-points. The samples were blotted on a PVDF membrane, washed with 0.1% trifluoroacetic acid, and subjected to automated Edman degradation. The molar amounts of intact LD78β (▴), LD78β(3-70) (●), and LD-78β(5-70) (■) present in the samples were calculated from the initial yields of the protein sequencer and are expressed as the percent of the total amount of LD78β.