Preparation of radioactive acetyl-l-carnitine by an enzymatic exchange reaction

A rapid method for the preparation of 1-¹⁴C]acetyl-l-carnitine is described. The method involves exchange of 1-¹⁴C]acetic acid into a pool of unlabeled acetyl-l-carnitine using the enzymes acetyl-CoA synthetase and carnitine acetyltransferase. After isotopic equilibrium is attained, radioactive acetylcarnitine is separated from the other reaction components by chromatography on Dowex 1 (Cl^?) anion exchange resin. One of the procedures used to verify the product 1-¹⁴C]acetyl-l-carnitine can be used to synthesize (3S)-5-¹⁴C]citric acid.