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 [(3)H]H2O space of red beet (Beta vulgaris L.) vacuoles has been studied using silicone-layer-filtering centrifugation on both fluorometric and (14)C-measurement of sucrose. Sucrose transport into vacuoles proceeds partly by an active transport system and partly by passive permeation. The K M(20°C) for active sucrose uptake was found to be about 22 mM and the V Max(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.