Enzymatic synthesis of L-[4-13C]aspartic acid

An efficient procedure for the production of l-[4-13C]aspartic acid (4-13C-Asp) was investigated. In this procedure, phosphoenolpyruvate carboxylase originating from the methanol-assimilating microbe, Methylobacterium extorquens JCM 2805, was used for the production of labeled oxaloacetic acid from phosphoenolpyruvate (PEP) and NaH13CO3; the oxaloacetic acid was then converted to 4-13C-Asp with glutamic-oxaloacetic transaminase. In this reaction, with starting concentrations of 10 mM PEP, 10 mM NaH13CO3 and 15 mM L-glutamic acid (Glu), the yield was 70%. 4-13C-Asp and Glu in the final reaction mixture were separated by displacement chromatography. The yield of this process was 84%. The overall yield was 59%. The incorporation of 13C at the C-4 position of 4-13C-Asp was confirmed by NMR spectroscopy.