Glutamate as a precursor for the pyrrolidine ring of nicotine.

Recently it has been demonstrated that the amino acid, ornithine, is an efficient precursor of the pyrrolidine ring of nicotine in the tobacco plant (1,2). Although there is considerable evidence that ornithine and glutamie acid may give rise to the pyrrolidine ring of proline through a common intermediate in animal systems (3) and in microorganisms (4), there has been little study of this metabolic relationship in higher plants. Morgan and Marion (5) isolated radioactive glutamic acid and proline from extracts of alfalfa plants that were fed C14-labeled ornithine. On the other hand, Naylor and Tolbert (6) reported no evidence of Cr4-labeled proline, ornithme, or arginine in leaves of barley seedlings after administration to the detached leaves of glutamic acid uniformly labeled with C14. Hence, it seemed of interest to test glutamic acid as a precursor of the pyrrolidine ring of nicotine in the tobacco plant. In the present work, glutamic acid-2-CY4, fed to tobacco plants, was found to be converted to radioactive nicotine. Degradation of the nicotine revealed that positions 2 and 5 of the pyrrolidine ring were focal points of C?4 labeling.