Biosynthesis of uniformly labeled 13C- and 14C-arachidonic acid in Mortierella alpina

- Procedures for the laboratory-scale preparation of U-13C-ARA and U-14C-ARA are described.
- The yield of U-13C-ARA was >100 nmol with an isotopic purity of 95%.
- The yield of U-14C-ARA was >2 μCi with an estimated specific activity of >1200 Ci/mol.
- Conversion efficiencies from glucose to ARA were 4-5%.
- Smaller quantities of other isotope-labeled fatty acids were also obtained.

Arachidonic acid (ARA) is one of the most abundant polyunsaturated fatty acids (PUFAs) in the mammalian brain. Many enzymatically- and nonenzymatically-produced metabolic products have important and potent pharmacological properties. However, uniformly isotope labeled forms of ARA are not commercially available for studying the metabolic fates of ARA. This study describes a simple and efficient protocol for the biosynthesis of U-13C-ARA from U-13C-glucose, and U-14C-ARA from U-14C-glucose by Mortierella alpina. The protocols yield approximately 100 nmol quantities of U-13C-ARA with an isotopic purity of 95% from a 500 μl batch volume, and approximately 2 μCi quantities of U-14C-ARA with an apparent specific activity in excess of 1200 Ci/mol from a 250 μl batch volume.