Biosynthesis tryptophan

Valine, leucine, and isoleucine biosynthesis Lysine biosynthesis Lysine degradation Arginine and proline metabolism Histidine metabolism Tyrosine metabolism Phenylalanine metabolism Tryptophan metabolism Phenylalanine, tyrosine, and tryptophan biosynthesis Urea cycle and metabolism of amino groups... 

Glucose breakdown and tryptophan biosynthesis illustrate pathways consisting of a linear series of reactions. In chapter 12 we will see that the glycolytic pathway also contains branches so that common intermediates can proceed along diverging routes after the branchpoint. We will also see that the glycolytic pathway is organized so that some of the reactions within the pathway can go in either the forward or the reverse direction. 

The tryptophan biosynthetic pathway in E. coli. There are five enzymatically catalyzed reactions involved in tryptophan biosynthesis and five different polypeptides associated with these reactions. Polypeptides E and D normally make a tetrameric complex, which... 

The first specific step in tryptophan biosynthesis is the glutamine-dependent conversion of chorismate to the simple aromatic compound anthranilate. Like most other glutamine-dependent reactions, the reaction can also occur with ammonia as the source of the amino group. However, high concentrations of ammonia are required. Thus far, almost all the anthranilate synthases examined have the glutamine amidotransferase activity (component II) and the choris-mate-to-anthranilate activity (component I) on separate proteins. 

In what sense may indole be viewed as an intermediate in L-tryptophan biosynthesis ... 

For several years, indole, which was accumulated by some mutants and used to satisfy the tryptophan requirement by others, was considered an intermediate in tryptophan biosynthesis. Such a role for indole would have been of interest, because it appeared to be an exception to the generalization that biosynthetic intermediates had to bear a charge. It was found that extracts of cells that utilized indole did indeed catalyze the condensation of indole with serine, and extracts of cells that accumulated indole catalyzed the... 

The trp operon contains a cluster of five structural genes associated with tryptophan biosynthesis. Initiation of transcription of the trp operon is regulated by a repressor protein that functions similarly to the lac repressor. The main difference is that the trp repressor action is subject to control by the small-molecule effector, tryptophan. When tryptophan binds the repressor, the repressor binds to the trp operator. Thus, the effect of the small-molecule effector here is opposite to its effect on the lac operon. When tryptophan is present, there is no need for the enzymes that synthesize tryptophan. 

Bischler-Napieralski reactions, 4, 279 carboline synthesis from, 4, 516 Mannich-type reactions, 4, 279 sulfur isosteres, biological activity, 4, 913 synthesis, 4, 337, 913 Tryptophan biosynthesis, 1, 264 carboline synthesis from, 4, 516 molecular structure, 4, 162 Tryptophan hydroxylase in serotonin biosynthesis, 1, 261 Tryptophan oxygenase... 

R. Sterner, Two (j3a)(8)-barrel enzymes of histidine and tryptophan biosynthesis have similar reaction mechanisms and common strategies for protecting their labile substrates, Biochemistry 2002, 41, 12032-120342. 

The trp operon contains five structural genes encoding enzymes for tryptophan biosynthesis, a trp promoter (Ptrp) and a trp operator sequence (Otrp). The operon is transcribed only when tryptophan is scarce. 

In the late 1990 s, a breakthrough in biosynthesis was reached based on the finding that benzoxazinone and tryptophane biosynthesis have a formal branch point, and indole is a precursor of the benzoxazinones.18 The biosynthetic pathway from indole as the precursor of the benzoxazinone moiety was elucidated both on the levels of the responsible gene cluster discovered and the corresponding enzymes.23 The stepwise oxidation of indole with molecular oxygen by means of... 

An effect opposite to induction is enzyme repression. Wild-type E. coli cells can be grown on a medium containing an ammonium salt as the sole source of nitrogen. Under these conditions, all nitrogenous compounds must be formed from ammonium ion and a carbon source, and such cells have all the enzymes necessary for the synthesis of the 20 amino acids requisite for protein synthesis. If, for example, the amino acid tryptophan is added to the culture medium, all the enzymes required for the biosynthesis of tryptophan disappear from the cell. In this case, the synthesis of five enzymes catalyzing five consecutive steps in tryptophan biosynthesis is repressed. This is a termed coordinate repression. It will become clear that induction and repression are manifestations of the same phenomenon. 

Scheme 14.4. Substrate specificities of ProFARI (involved in histidine biosynthesis) and PRAI (involved in tryptophan biosynthesis).

Wilmanns, M., Hyde, C. C., Davies, D. R., Kirschener, K., and Jansonius, J. N., 1991, Structural conservation in parallel beta/alpha barrel enzymes diat catalyse diree sequential reactions in the pathway of tryptophan biosynthesis. Biochemistry 30 9161n9169. 

Gollnick P, Babitzke P, Antson A, Yanofsky C. Complexity in regulation of tryptophan biosynthesis in Bacillus subtilis. Annu. Rev. Genet. 2005 39 47-68. 

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