Stereochemistry of the glutamate mutase reaction.

4-Deuterioglutamic acid was prepared by incubation in DzO of ammonium mesaconate with an extract of Clostri&urn tetanomorphum. In these extracts, methylaspartase catalyzed the formation of threo-3-methyl-L-aspartate-3-D, which was then rearranged to glutamate by the cobamide coenzyme-dependent glutamate mutase. The monodeuteriosuccinate obtained by chloramine-T oxidation of the glutamate showed a plain negative optical rotatory dispersion curve, and was therefore (R)-succinate-2-D. It was concluded that the intramolecular rearrangement of thero-3-methyl-L-aspartate to L-glutamate proceeded by net inversion of configuration of carbon atom 3. (R)-Succinate-2-D was also prepared from (2S,3R)-aspartic acid3-D.