IDENTIFICATION OF THE STEREOISOMERIC CONFIGURATIONS OF METHYLCITRIC ACID PRODUCED BY SI-CITRATE SYNTHASE AND METHYLCITRATE SYNTHASE USING CAPILLARY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

The absolute separation of the four stereoisomeric configurations of m ethylcitric acid can be achieved on a nonchiral stationary phase SE30 capillary column using the corresponding O-acetylated (tri-(-)-2-butyl ester derivatives. Identification of the separated isomers was done u sing methylcitric acid produced by si-citrate synthase and methylcitra te synthase of Candida lipolitica. si-Citrate synthase produces the (2 S,3S)-, (2S,3R)- and a small amount of the (2R,3S)-isomers. Methylcitr ate synthase produces the (2R,3S)-isomer, indicating that this enzyme is more stereospecific than the animal citrate synthase enzyme. The (2 R,3R)-isomer may act as an inhibitor of aconitase.