Physiological study of ergot: induction of alkaloid synthesis by tryptophan at the enzymatic level.
The enhancement of ergot alkaloid production by tryptophan and its analogues in both normal and high-phosphate cultures is more directly related to increased dimethylallyltryptophan (DMAT) synthetase activity rather than to a lack of regulation of the tryptophan biosynthetic enzymes. Thiotryptophan [beta-(1-benzo-thien-3-yl)-alanine] is rather ineffective in the end product regulation of tryptophan biosynthesis, whereas tryptophan and 5-methyltryptophan are potent effectors. The presence of increased levels of DMAT synthetase in ergot cultures supplemented with tryptophan or thiotryptophan, and to a lesser extent with 5-methyltryptophan, suggests that the induction effect involves de novo synthesis of the enzyme. Thiotryptophan and tryptophan but not 5-methyltryptophan can overcome the block of alkaloid synthesis by inorganic phosphate. The results with thiotryptophan indicate that the phosphate effect cannot be explained merely on the basis of a block of tryptophan synthesis.
D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000378:metabolism; D000878:Anthranilate Synthase / Q000378:metabolism; D002474:Cell-Free System; D002967:Claviceps / Q000201:enzymology / Q000378:metabolism*; D004790:Enzyme Induction; D004876:Ergot Alkaloids / Q000096:biosynthesis*; D010710:Phosphates / Q000494:pharmacology; D014166:Transferases / Q000378:metabolism; D014364:Tryptophan / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism*; D014367:Tryptophan Synthase / Q000378:metabolism
D004876:Ergot Alkaloids; D010710:Phosphates; D014364:Tryptophan; D014166:Transferases; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D000878:Anthranilate Synthase; D014367:Tryptophan Synthase