Pipecolic Acid Biosynthesis in Rhixoctonia leguminicola OXIDASE: A UNIQUE FLAVIN ENZYME INVOLVED IN PIPECOLIC ACID BIOSYNTHESIS*

The fungal parasite Rhizoctonia leguminicola produces two indolizidine alkaloids, slaframine and swainsonine, of physiological interest. These alkaloids are biosynthesized from pipecolic acid which in turn is derived from L-lysine in this fungus as shown in the accompanying paper (Wickwire, B. M., Harris, C. M., Harris, T. M., and Broquist, H. P. (1989) J. Biol. Chem. 265, 14742-14747): L-lysine + saccharopine + A’piperideine-6-carboxylate + pipecolate. This paper concerns the discovery, purification, and properties of a flavoenzyme, termed saccharopine oxidase, which carries out the oxidative cleavage of saccharopine as follows: