Characteristics of transport of L-leucine and glycine in pea protoplasts

Abstract

The uptake of L - leucine and glycine into pea protoplasts was studied under various conditions. The uptake of both L - leucine and glycine was pH dependent with the optimal pH being 4.0 and 5.0 for L - leucine and glycine, respectively. A kinetic study of L - leucine uptake showed that uptake is multiphasic; K_m values of different phases were 1.1 mol m^-3, 33.3 mol m^-3 and 100 mol m³. A similar analysis for glycine at a concentration range of 0.1-10 mol m^-3 also showed a multiphasic transport system for it. The uptake of L - leucine at lower concentrations(between 0.1 - 2.0 mol m^-3) was energy dependent, since arsenate, azide, dinitrophenol and iodoacetate inhibited the uptake. However, the uptake of L - leucine was not inhibited by ouabain at any concentration of L - leucine employed. The uptake of glycine was not inhibited by any of these inhibitors suggesting that glycine uptake was not mediated by an active process.