Allylglycine, and inhibitor of the uptake of L-leucine and L-proline in rat brain slices

The convulsant allylglycine inhibited the uptake of l-leucine and l-proline in rat brain slices and was without influence on the uptake of acetylcholine, dopamine, l-glutamic acid, glycine and l-lysine under the conditions studied. l-Leucine uptake could also be inhibited by the “large neutral” amino acids l-methionine, l-phenylalanine and l-valine. No kinetic studies of l-leucine uptake were possible due to the inability to measure initial rates of uptake. The time course of l-leucine uptake was not linear under a variety of conditions and appeared to be complicated by a rapid efflux of radioactive label in the form of acidic metabolite(s). l-Proline uptake was mediated by a “high affinity” saturable system (K_m 50 μM), and was non-competitively inhibited by allylglycine (K_i{ca.} 50 μM). l-Leucine competitively inhibited (K_i, 75 μM) l-proline uptake, although l-leucine uptake was unaffected by l-proline. l-Norleucine, DL-pipecolic acid and l-azetidine-2-carboxylic acid inhibited l-proline uptake.