Determination of the kinetic properties of platycodin D for the inhibition of pancreatic lipase using a 1,2-diglyceride-based colorimetric assay.

A 1,2-diglyceride-based multi-step colorimetric assay to measure the pancreatic lipase activity was applied for the determination of the kinetic profiles of the lipase inhibition with a slight modification and the validity verification. With this assay method, our study revealed that platycodin D, one of major constituents of Platycodi Radix, inhibits the pancreatic lipase activity in a competitive type, with the value of KI being 0.18+/-0.02 mM. In addition, PD has affected the values of K(m,app) and Kcat/Km in a dose-dependent manner. The results shed a meaningful light on how PD mediates lipid metabolism in the intestinal tracts. On the other hand, since the revised assay is sensitive, rapid, and does not affect the accuracy to the kinetic properties, it is applicable not only to evaluation of the kinetic properties of the pancreatic lipase, but also to high-throughput screening of pancreatic lipase activity.