Enzymatic Synthesis Of Some N-15-Labelled L-Amino Acids

Our group has developed a stereospecific enzymatic method, which is very efficient for the in vitro synthesis of L-[N-15]serine, L-[15N]methionine and L-[15N]glutamic acid. These amino acids were prepared from the corresponding alpha-ketoacids in the suitable enzymatic systems. The bacterial NAD-dependent amino acid dehydrogenases alanin dehydrogenase, leucin dehydrogenase and glutamate dehydrogenase were used as catalysts. Glucose dehydrogenase was used for the regeneration of NADH and (NH4Cl)-N-15 as isotopically labelled material at 99 at.% N-15. All reactions are inexpensive and easy to perform on a synthetically useful scale (1-10g) giving high yields of L-amino acids. The N-15 isotope content was determined by mass spectrometry.