Repression and inhibition of indole-synthesizing activity in Neurospora crassa.
Lester, Gabriel (Worcester Foundation for Experimental Biology, Shrewsbury, Mass.). Repression and inhibition of indole-synthesizing activity in Neurospora crassa. J. Bacteriol. 82:215-223. 1961.-The possibility of repression and feedback inhibition as regulating mechanisms for the synthesis of tryptophan by Neurospora crassa has been examined in a tryptophan auxotroph which accumulates indole (and indole-glycerol). Indole-synthesizing activity was determined with germinated conidia suspended in medium lacking tryptophan. This activity was almost absent from cells cultured on germination medium containing more than 1.0 mumole l-tryptophan per ml, and increased with decreasing concentrations of l-tryptophan. A similar depression of the formation of indole synthesizing activity was caused by 6-methyl- and d-tryptophan, and less effectively by 5-methyltryptophan; 4-methyltryptophan was slightly stimulatory. Preformed indole synthesizing activity was inhibited by l-tryptophan, 4- and 6-methyltryptophan, and to a lesser extent by 5-methyltryptophan; d-tryptophan had no effect in this respect. The inhibition of preformed activity was partially reversed by anthranilic acid, which is a precursor of indole. However, anthranilic acid did not increase indole synthesis by cells wherein the formation of indole-synthesizing activity had been depressed by culture in the presence of high concentrations of l- or d-tryptophan. These observations indicate that regulation of tryptophan synthesis in N. crassa might result from the action of tryptophan as a repressor and as a feedback inhibitor. The relation of these results to other regulatory systems is discussed.
D007211:Indoles / Q000378:metabolism*; D009491:Neurospora / Q000378:metabolism*; D009492:Neurospora crassa; D014364:Tryptophan / Q000378:metabolism* / Q000031:analogs & derivatives; D062367:ortho-Aminobenzoates
D007211:Indoles; D062367:ortho-Aminobenzoates; C031385:anthranilic acid; C082802:4-methyltryptophan; C004182:5-methyltryptophan; C028129:tryptophan methyl ester; C030374:indole; D014364:Tryptophan
INDOLES/metabolism; NEUROSPORA/metabolism; TRYPTOPHAN/metabolism