Preparation of 15N-labeled l-aspartic acid using whole bacteria as enzyme source

Stereoselective synthesis of L‐[15N] amino acids with glucose dehydrogenase and galactose mutarotase as NADH regenerating system

“…Chemicals 15 NH 4 Cl 99 at.% 15 N was produced at the National Institute for Research and Development of Isotopic and Molecular Technologies, Cluj-Napoca, Romania. The various a-keto acids mentioned in this paper were purchased from Sigma.…”

“…Among the various methods proposed for the synthesis of naturally occurring amino acids, the enzymatic procedures, being stereospecific, are the most frequently used. Thus, by coupling the reaction catalysed by one of the well-characterized amino acid dehydrogenases (glutamate-, alanine-, leucine-or phenylalanine dehydrogenase) with a NADH generating reaction (glucose-6-phosphate/glucose-6-phosphate dehydrogenase; ethanol/alcohol dehydrogenase; lactate/lactate dehydrogenase; formic acid/formate dehydrogenase) ten proteinogenic L-amino acids labelled with 15 N can be produced from millimolar to molar scale. [6][7][8][9][10] The required specific enzymes could be obtained currently at low cost by recombinant DNA technology.…”

“…[1][2][3] On the other hand they have served for more than two decades in determining the three-dimensional structure of proteins by heteronuclear NMR spectroscopy. 4,5 Although several L-amino acids labelled with 15 N are commercially available, some of them such as L- [ 15 N]-methionine or L- [ 15 N]-serine are still prohibitively expensive. Among the various methods proposed for the synthesis of naturally occurring amino acids, the enzymatic procedures, being stereospecific, are the most frequently used.…”