XVI International Botanical Congess
The fate of homoserine (an intermediate in the synthesis of aspartame-derived amino acids) was characterized in heterotrophic suspension cells. Homoserine actively entered the cells in competition with serine, via a high affinity proton-symport carrier (Km˜50-60µM, Vmax = 8 ± 0.5 µmol/h/g cell wet weight). 31P-NCR and 13C-NCR permitted to follow the metabolism of homoserine to phosphohomoserine and threonine. Using in vivo 13C-NCR we could visualize the compart mentation of hemoserine: it accumulated at a concentration 4-5 time higher in the cytoplasm than in the large vacuole. This technique was further utilized to analyze the subcellular compart mentation of proline in leaves of Pringlea anticorbutica R. Br. (Kerguelen cabbage), a subantarctic Brassicaceae accumulating proline as a major solute upon salt stress.