STUDIES ON THE BIOSYNTHESIS OF ERGOT ALKALOIDS

Abstract

DL-Tryptophan-β-C¹⁴, but not L-phenylalanine-U-C¹⁴ nor L-tyrosine-U-C¹⁴, is incorporated into the ergoline moiety of the ergot alkaloids. The high specific activities of the bases isolated from cultures supplemented with a mixture of DL-tryptophan-β-C¹⁴and carrier L-tryptophan indicate some contribution from the D-isomer.L-Phenylalanine-U-C¹⁴ serves as a precursor of the lysergic acid and isolysergic acid derivatives which contain this amino acid in their peptide moieties. L-Tyrosine-U-C¹⁴ is not a precursor. The distribution of activity in the cultures at the end of the growth phase suggests that, in the strain of Claviceps purpurea used in these investigations, none of these aromatic amino acids is extensively degraded. All are incorporated directly into cell protein. A portion of the phenylalanine is hydroxylated to tyrosine and this pathway appears to be of major importance in tyrosine biosynthesis. All three of the amino acids were incorporated extensively into a red-brown pigment which is probably a polymer of the quinone – amino acid type.Under the conditions used in these experiments small but significant amounts of mevalonic acid-2-C¹⁴ and formic acid-C¹⁴ were used in alkaloid biosynthesis.