Improved Biotransformation of Platycoside E into Deapiose-Xylosylated Platycodin D by Cytolase PCL5 under High Hydrostatic Pressure

Abstract

Platycosides are the functional saponins present in balloon flowers that exert diverse biological effects, and which can be further improved by their deglycosylation. Deapiose-xylosylated platycodin D, which is absent in balloon flowers, can be generated only by cytolase PCL5 by acting on platycoside E. To improve cytolase PCL5-catalyzed production of deapiose-xylosylated platycodin D from platycoside E, we explored the use of high hydrostatic pressure (HHP). At an HHP of 150 MPa, the optimal temperature of cytolase PCL5 activity for converting platycoside E into deapiose-xylosylated platycodin D shifted from 50 to 55 °C, and increased the activity and stability of the enzyme by 5- and 4.9-fold, respectively. Under HHP, the enzyme completely converted 1 mM platycoside E into deapiose-xylosylated platycodin D within 4 h, with a 3.75-fold higher productivity than that under atmospheric pressure. Our results suggest that the application of HHP is a potential method for the economical production of platycosides and enzyme-catalyzed biotransformation of functional saponins.