tryptophan

locus: trp

locus_name: tryptophan

organism_type: B

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cultural_requirements: Tryptophan is required in much higher concentrations than its precursors, anthranilic acid and indole. A 0.01-mg/ml amount of the precursor is sufficient, but up to 0.1 or 0.2 mg of tryptophan per ml is required by some mutants. High concentrations of anthranilic acid are toxic. Most trp mutants grow better on 0.2 mg of tryptophan per ml plus 0.2 mg of phenylalanine per ml than on tryptophan alone. For the biosynthetic pathway, see Fig. 11. Also called tryp and try. trp-3 called td. See also nt. Tryptophan feedback inhibits anthranilate synthase, anthranilate phosphoribosyltransferase, and one of three isozymes of 3-deoxy-D-arabinoheptulosonic acid-7-phosphate synthase (the first step in aromatic biosynthesis). Tryptophan stimulates chorismate mutase, directing chorismate to prephenate rather than to anthranilate synthesis. All four genes of the tryptophan pathway are derepressed by starvation for tryptophan. High indoleglycerol-phosphate levels also cause derepression. Derepression may involve inhibition of Trp-tRNA synthetase. (40, 152, 258, 436, 603, 742, 1004, and references therein). Genes for tryptophan biosynthesis are derepressed coordinately with those for histidine, arginine, and lysine biosynthesis; this is called "cross-pathway regulation" (137, 1131); reviewed in reference 642; see cpc-1.

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supplement: tryptophan

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Strains

References