CHARACTERISTICS OF THE SUCROSE UPTAKE SYSTEM OF VACUOLES ISOLATED FROM RED BEET TISSUE - KINETICS AND SPECIFITY OF THE SUCROSE UPTAKE SYSTEM

The uptake of sucrose against a concentration gradient into the dextran-impermeable [3H]H2O space of red beet (Beta vulgaris L.) vacuoles has been studied using silicone-layer-filtering centrifugation on both fluorometric and 14C-measurement of sucrose. Sucrose transport into vacuoles proceeds partly by an active transport system and partly by passive permeation. The KM(20°C) for active sucrose uptake was found to be about 22 mM and the VMax(20°C) was about 174 nmol sucrose x (unit betacyanin)-1 x h-1. The temperature dependency of sucrose transport appears to have an activation energy of 35,0 KJ×mol-1. Among various mono-, di-, and trisaccharides tested, raffinose acts as a competitive inhibitor of sucrose uptake. © 1979 Springer-Verlag.