Effect of triton X-100 on the electrophoretic mobility of solubilized intestinal brush border membrane dipeptidyl peptidase IV.

Dipeptidyl peptidase IV (dipeptidylpeptide hydrolase, EC 3.4.14.-) was solubilized from a rat intestinal mucosal brush border membrane preparation in varying concentrations of Triton X-100. Samples of a solubilized supernatant fraction were subjected to polyacrylamide gel electrophoresis, and the activities of several brush border enzymes were measured in gel slices following elution of the enzymes from the gel. At low concentrations of Triton X-100 (0.5%), two peaks of dipeptidyl peptidase IV activity were observed suggesting the presence of two electrophoretically distinct enzymes. However with increasing Triton X-100 concentrations, the slower migrating species was converted to a faster migrating form and only one major band of activity was observed at 10% Triton. These results indicate that there is only one form of the enzyme and that care must be taken when interpreting the electrophoretic patterns of detergent solubilized membrane bound enzymes.