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.