Enzymatic preparation of radiolabeled succinic semialdehyde

[U-14C]Succinic semialdehyde was prepared with yields of 30-40% by oxidation of purified [U-14C]4-aminobutyric acid with commercially available bovine plasma monoamine oxidase. [U-14C]Succinic semialdehyde was purified by cation-exchange chromatography and quantified as the oxime and methoxime derivatives using liquid partition chromatography on silicic acid. The availability of [U-14C]succinic semialdehyde permits the reliable assay of succinic semialdehyde dehydrogenase in crude cell extracts of lymphocytes isolated from human blood, cultured human lymphoblasts, and other tissues where 4-aminobutyric acid metabolism is known to occur.