THE IMMEDIATE PRECURSOR OF THE NITROGEN-CONTAINING RING OF RAPAMYCIN IS FREE PIPECOLIC ACID

Studies were carried out to determine the precursor of the nitrogen-co ntaining ring of rapamycin. The addition of L-lysine and D,L-pipecolat e to the medium of Streptomyces hygroscopicus did not affect the speci fic production of rapamycin. In a basal medium containing no L-lysine except for that in the yeast extract component, L-C-14-lysine and D,L- H-3-pipecolate were incorporated to a high degree into rapamycin, D,L- H-3-pipecolate being incorporated at a higher efficiency. Unlabeled pi pecolate reduced the incorporation of radioactive lysine much more tha n unlabeled lysine decreased the incorporation of radioactive pipecola te. These results indicate that pipecolate is the more direct precurso r of rapamycin, lysine being converted to pipecolate and free pipecola te being incorporated directly into rapamycin. Rapamycin samples enric hed with C-14-lysine and H-3-pipecolate were hydrolyzed and analyzed t o provide evidence of specific incorporation of these precursors into the pipecolate moiety.