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PubMed2000

Some tryptophan pathways in the phytopathogen Xanthomonas oryzae pv. oryzae.

Xanthomonas oryzae pv. oryzae, the causal organism of bacterial blight of rice which produces leaf blight as well as kresek (wilt) symptoms in plants were tested for indole, auxin production in culture supplemented with L-tryptophan. On the basis of indoleacetic acid (IAA) production the isolates were grouped into IAA-positive and IAA-negative. Out of 17 isolates, 11 were IAA-positive while 6 were IAA-negative. The isolates metabolized tryptophan through two different routes and the isolates vary in the pathway of tryptophan utilization. The IAA-positive isolates converted tryptophan to IAA as the end product, whereas the IAA-negative isolates formed anthranilate as an intermediate metabolite and finally produced pyrocatechol via the kynurenine pathway. Quantification of tryptophan metabolism revealed that the maximum production of IAA and pyrocatechol in culture occurred during 2-d incubation at 30 +/- 2 degrees C.

Catechols↗
PubMed1993

p-Aminobenzoate synthesis in Escherichia coli: mutational analysis of three conserved amino acid residues of the amidotransferase PabA.

p-Aminobenzoate synthesis in Escherichia coli requires three enzymes, PabA, PabB, and PabC, acting respectively as glutaminase, chorismate aminase, and 4-amino-4-deoxychorismate aromatase. PabA requires stoichiometric amounts of PabB to display glutaminase activity. PabA has conserved cysteine (C79), histidine (H168), and glutamate (E170) residues that have been suggested in the analogous anthranilate synthase to form a type of catalytic triad in an acylenzyme mechanism. Mutations at each of these residues of PabA lead to the following observations. C79S PabA has 40-fold lower kcat and 10(4) lower kcat/Km with no detectable acylenzyme accumulation in steady-state turnover (vs wild-type PabA at 0.56 mol fraction of gamma-glutamyl-enzyme). H168Q has no catalytic activity and does not compete with wild-type PabA for PabB (this may indicate a folding defect). Four E170 mutants give three outcomes. E170D and E170A yield active PabA species, down 4-fold and 150-fold, respectively, in kcat/Km ratios from wild-type PabA. E170Q has no detectable glutaminase activity but does bind to PabB in competition with wild-typoe PabA while E170K has neither detectable catalytic activity nor the ability to be recognized by PabB.

4-Aminobenzoic Acid↗
PubMed1989

Cloning and expression of a trypomastigote-specific 85-kilodalton surface antigen gene from Trypanosoma cruzi.

An 85-kDa trypomastigote-specific surface antigen gene from Trypanosoma cruzi has been identified by screening a genomic library in lambda gt10 with trypomastigote and epimastigote cDNA. The 1.3-kb genomic clone (pTt34) hybridizes to a single trypomastigote mRNA of 3.7 kb and to multiple bands in genomic Southern blots. Dot-blot experiments show that there are 5-10 copies of this sequence per haploid genome, and these are arranged in a non-tandem manner. pTt34 has been expressed as an anthranilate synthetase fusion protein in Escherichia coli, and inclusion bodies have been used to raise antiserum in rabbits. This antiserum immunoprecipitates a cell surface trypomastigote-specific protein of 85 kDa. The DNA and predicted amino acid sequences of pTt34 are given. Four further clones obtained from a PvuII/HpaI partial genomic library in pUC13 have extended the sequence of the 3' end of pTt34; each of these clones has regions of sequence divergence and each could represent a different member of the gene family.

Amino Acid Sequence↗
PubMed2003

Tandem transcription and translation regulatory sensing of uncharged tryptophan tRNA.

The Bacillus subtilis AT (anti-TRAP) protein inhibits the regulatory protein TRAP (trp RNA-binding attenuation protein), thereby eliminating transcription termination in the leader region of the trp operon. Transcription of the AT operon is activated by uncharged tryptophan transfer RNA (tRNATrp). Here we show that translation of AT also is regulated by uncharged tRNATrp. A 10-residue coding region containing three consecutive tryptophan codons is located immediately preceding the AT structural gene. Completion of translation of this coding region inhibits AT synthesis, whereas incomplete translation increases AT production. Tandem sensing of uncharged tRNATrp therefore regulates synthesis of AT, which in turn regulates TRAP's ability to inhibit trp operon expression.

Anthranilate Synthase↗
PubMed1994

Enediyne-mediated DNA damage in nuclei is modulated at the level of the nucleosome.

DNA damage in HeLa nuclei and isolated nucleosome core particles has been examined for several members of the enediyne family of antitumor antibiotics: calicheamicin gamma 1I (CAL), esperamicin A1 (ESP A1), esperamicin C (ESP C), and neocarzinostatin (NCS). In nuclei, both NCS and ESP A1 produced DNA damage limited to the linker region of the nucleosome, while CAL and ESP C, an analog of ESP A1 missing the deoxyfucose-anthranilate moiety, damaged both the core and linker DNA. DNA fragments produced by CAL and ESP C in the nucleosome core occurred with a 10-11-nucleotide periodicity similar to that produced by DNase I, while damage produced by NCS and ESP A1 appeared to be limited to the terminal portions of the core DNA. The damage in nuclei is shown to be caused directly by the drugs with little contribution from endogenous factors, such as nucleases and topoisomerases. Features of drug structure that may limit damage to the nucleosome core include the presence of substituents on both sides of the CAL/ESP-type core, and the presence of an intercalating moiety, such as the naphthoate of NCS and possibly the anthranilate of ESP A1.

Aminoglycosides↗
PubMedDate not supplied

[Differential expression of recombinant hybrid proteins containing amino- and carboxy-terminal regions of the exterior large glycoprotein (gp46) of the human T-cell leukemia virus (HTLV-I) in Escherichia coli cells].

Plasmid clones capable of expressing a recombinant fusion proteins containing the anthranilate synthase of E. coli (TrpE) and different regions of gp46 HTLV-I were constructed on the basis of pATH-vectors. A high extent of TrpE-gp46 proteolytic degradation took place independently of the bacterial La-protease. Fusion proteins containing an N-terminal part of gp46 were more stable and could be purified in preparative quantities but were less antigenic. On the contrary, a TrpE-gp46 protein encoded by the TaqI-TaqI DNA fragment and containing only 35 C-terminal amino acids was still susceptible to degradation but possessed good serologic reactivity. Some of the recombinant proteins obtained can be useful for diagnostics and for preparing monoclonal or polyclonal antibodies.

Anthranilate Synthase↗
PubMed1992

The maize auxotrophic mutant orange pericarp is defective in duplicate genes for tryptophan synthase beta.

orange pericarp (orp) is a seedling lethal mutant of maize caused by mutations in the duplicate unlinked recessive loci orp1 and orp2. Mutant seedlings accumulate two tryptophan precursors, anthranilate and indole, suggesting a block in tryptophan biosynthesis. Results from feeding studies and enzyme assays indicate that the orp mutant is defective in tryptophan synthase beta activity. Thus, orp is one of only a few amino acid auxotrophic mutants to be characterized in plants. Two genes encoding tryptophan synthase beta were isolated from maize and sequenced. Both genes encode polypeptides with high homology to tryptophan synthase beta enzymes from other organisms. The cloned genes were mapped by restriction fragment length polymorphism analysis to approximately the same chromosomal locations as the genetically mapped factors orp1 and orp2. RNA analysis indicates that both genes are expressed in all tissues examined from normal plants. Together, the biochemical, genetic, and molecular data verify the identity of orp1 and orp2 as duplicate structural genes for the beta subunit of tryptophan synthase.

Amino Acid Sequence↗
PubMed1969

Temperature-sensitive repression of the tryptophan operon in Escherichia coli.

Mutants of Escherichia coli exhibiting temperature-sensitive repression of the tryptophan operon have been isolated among the revertants of a tryptophan auxotroph, trpS5, that produces an altered tryptophanyl transfer ribonucleic acid (tRNA) synthetase. Unlike the parental strain, these mutants grew in the absence of tryptophan at high but not at low temperature. When grown at 43.5 C with excess tryptophan (repression conditions), they produced 10 times more anthranilate synthetase than when grown at 36 C or lower temperatures. Similar, though less striking, temperature-sensitivity was observed with respect to the formation of tryptophan synthetase. Transduction mapping by phage P1 revealed that these mutants carry a mutation cotransducible with thr at 60 to 80%, in addition to trpS5, and that the former mutation is primarily responsible for the temperature-sensitive repression. These results suggest that the present mutants represent a novel type of mutation of the classical regulatory gene trpR, which probably determines the structure of a protein involved in repression of the tryptophan operon. In agreement with this conclusion, tRNA of several trpR mutants was found to be normal with respect to its tryptophan acceptability. It was also shown that the trpS5 allele, whether present in trpR or trpR(+) strains, produced appreciably higher amounts of anthranilate synthetase than the corresponding trpS(+) strains under repression conditions. This was particularly true at higher temperatures. These results provide further evidence for our previous conclusion that tryptophanyl-tRNA synthetase is somehow involved in repression of this operon.

Chromosome Mapping↗
PubMed2005

Characterization of tryptophan-overproducing potato transgenic for a mutant rice anthranilate synthase alpha-subunit gene (OASA1D).

Potato plants (Solanum tuberosum cv. May Queen) transgenic for OASA1D, which encodes a point mutant of an alpha-subunit of rice (Oryza sativa) anthranilate synthase (AS, EC 4.1.3.27), were generated in order to determine the effects of the mutant gene on levels of free tryptophan (Trp) and AS activity in this important crop. Expression of OASA1D in potato induced a 2- to 20-fold increase in the amount of free Trp. This increase was likely due to a reduction in the sensitivity of AS containing the mutant alpha-subunit to feedback inhibition by Trp. Nontargeted metabolite profiling by high-performance liquid chromatography coupled with ultraviolet photodiode array detection as well as targeted profiling by liquid chromatography coupled with mass spectrometry revealed no marked changes in the levels of other metabolites, with the exception of indole-3-acetic acid (IAA), in the transgenic plants. The level of IAA in the upper part of the shoot was increased by a factor of 8.3-39, depending on the transgenic lines, with no detectable effect on plant growth or development. The effects of transformation thus appeared limited to the biosynthesis of Trp and IAA, with the overall metabolic network in potato being virtually unaffected. These results suggest that transformation with OASA1D may prove effective for the breeding of crops with an increased level of free Trp.

Anthranilate Synthase↗
PubMed1982

A new class of heterocyclic serine protease inhibitors. Inhibition of human leukocyte elastase, porcine pancreatic elastase, cathepsin G, and bovine chymotrypsin A alpha with substituted benzoxazinones, quinazolines, and anthranilates.

The serine proteases human leukocyte (HL) elastase, porcine pancreatic elastase, cathepsin G, and bovine chymotrypsin A alpha are inhibited competitively at pH 7.5 by heterocyclic compounds such as 2-substituted 4H-3,1-benzoxazin-4-ones, 4-quinazolines, and 4-chloroquinazolines, N-substituted phthalimides, and by thioesters of N-acylanthranilic acids. The most potent inhibitors have KI values in the 10(-7)--10(-8) M range. The inhibitors with fluoroalkyl or fluoroacyl substituents are much more potent than the alkyl or acyl derivatives. The quinazolinones, chloroquinazolines, and N-substituted phthalimides are quite specific for HL elastase. With HL elastase, an excellent correlation is observed between pKI and the infrared carbonyl-stretching frequency of the inhibitor. It is proposed that the partially polarized carbonyl group of the inhibitor interacts with a partially polarized charge relay system of the serine protease. The substituents on the inhibitors are proposed to interact with the primary substrate binding site of the serine proteases. The results indicate that it is possible to develop non-peptide small molecules which are specific inhibitors for HL elastase.

Animals↗
PubMed1986

Drug-binding properties of rat alpha-foetoprotein. Specificities of the phenylbutazone-binding and warfarin-binding sites.

Rat alpha-foetoprotein (alpha-FP) strongly binds the drugs warfarin and phenylbutazone, as does albumin; however, the binding sites for the two drugs seemed to be different. This possibility and the specificity of this/these drug-binding site(s) of rat alpha-FP were investigated by competitive protein-binding experiments with a variety of drugs, representing different pharmacological groups, and biomolecules that are strongly bound by the foetal protein and that are suspected to play a specific role during foetal development. The binding mechanisms were further investigated by using comparisons between computer-derived theoretical displacement curves and experimental points in order to distinguish different possible binding models. The results indicate: that warfarin and phenylbutazone are bound at two distinct sites on rat alpha-FP and that a negative modulatory effect is exerted between the two sites; that the degree of specificity of these two drug-binding sites is different, since the warfarin-binding site appears to be specific for the binding of coumarinic and anthranilic drugs whereas that for phenylbutazone is able to bind substances of very varied chemical structure and is more hydrophobic; that the phenylbutazone-binding site is the site that binds oestrogens that thyroid hormones and, probably, fatty acids and bilirubin are bound at (an)other site(s) but exert negative modulatory effects on phenylbutazone binding. The nature of the different binding areas of rat alpha-FP is compared with that of those already proposed for albumin. The potential risks of toxicity of such interactions between drugs and/or biomolecules on foetal development are also discussed.

Animals↗
PubMed1970

Physiological and kinetic studies with anthranilate synthetase of Bacillus alvei.

Anthranilate synthetase from Bacillus alvei was partially purified by ammonium sulfate fractionation and was stabilized by glycerol. The reaction mechanism of the enzyme was found to be sequential with respect to substrate, and the enzyme formed a hydroxamic acid in the absence of Mg(++). The K(m) for chorismic acid was 1.25 x 10(-4)m, and the K(m) for l-glutamine was 5.5 x 10(-4)m. Enzyme activity was inhibited by tryptophan noncompetitively with respect to chorismic acid and uncompetitively with respect to l-glutamine. An analysis of the inhibition patterns indicated that tryptophan may act as a dead end inhibitor and bind at the catalytic site. Enzyme activity could be completely inhibited in vitro and in vivo under the appropriate conditions, and enzyme synthesis was sensitive to repression by tryptophan. A sedimentation coefficient of 5.5S and an estimated molecular weight of 90,000 were obtained for the enzyme.

Bacillus↗
PubMed1969

Anthranilate synthetase, an enzyme specified by the tryptophan operon of Escherichia coli: purification and characterization of component I.

A procedure employed in the purification of anthranilate synthetase component I of Escherichia coli is described. The purified component appears homogeneous by starch gel electrophoresis and by sedimentation analysis. A molecular weight of 60,000 was estimated by gel filtration of Sephadex G-100. This value is consistent with the molecular weight estimated from the sedimentation and diffusion coefficients. Purified anthranilate synthetase component I cannot use glutamine as substrate and thus has no activity in the reaction of chorismate + l-glutamine --> anthranilate; however, it is active when ammonium sulfate is provided as amino donor. Sucrose density gradient analyses showed that ammonium sulfate does not affect the sedimentation velocity of component I. The ultraviolet absorption and fluorescence spectra of the purified component indicated that it contains tryptophan. Peptide pattern and extract complementation evidence suggested that the protein is a single polypeptide chain. Enzyme activity measurements indicated that wild-type E. coli produces equimolar amounts of at least four of the five polypeptides specified by the operon. Purified anthranilate synthetase component I is inhibited by l-tryptophan.

Centrifugation, Density Gradient↗
PubMed1974

Temperature-induced derepression of tryptophan biosynthesis in a tryptophanyl-transfer ribonucleic acid synthetase mutant of Bacillus subtilis.

A tryptophanyl-transfer ribonucleic acid (tRNA) synthetase (l-tryptophan: tRNA ligase adenosine monophosphate, EC 6.1.1.2) mutant (trpS1) of Bacillus subtilis is derepressed for enzymes of the tryptophan biosynthetic pathway at temperatures which reduce the growth rate but still allow exponential growth. Derepression of anthranilate synthase in a tryptophan-supplemented medium (50 mug/ml) is maximal at 36 C, and the differential rate of synthesis is 600- to 2,000-fold greater than that of the wild-type strain or trpS1 revertants. A study of the derepression pattern in the mutant and its revertants indicates that the 5-fluorotryptophan recognition site of the tryptophanyl-tRNA synthetase is an integral part of the repression mechanism. Evidence for a second locus, unlinked to the trpS1 locus, which functions in the repression of tryptophan biosynthetic enzymes is presented.

Amino Acyl-tRNA Synthetases↗
PubMed1990

Evolution of aromatic amino acid biosynthesis and application to the fine-tuned phylogenetic positioning of enteric bacteria.

A comprehensive phylogenetic tree for virtually the entire assemblage of enteric bacteria is presented. Character states of aromatic amino acid biosynthesis are used as criteria, and the results are compared with partial trees based upon sequencing of 16S rRNA, 5S rRNA, and tryptophan leader peptide. Three major clusters are apparent. Enterocluster 1 possesses a gene fusion (trpG-trpD) encoding anthranilate synthase: anthranilate 5-phosphoribosylpyrophosphate phosphoribosyltransferase of tryptophan biosynthesis. This cluster includes the genera Escherichia, Shigella, Citrobacter, Salmonella, Klebsiella, and Enterobacter. The remaining two clusters lack the trpG-trpD gene fusion, but differ in the presence (enterocluster 2) or absence (enterocluster 3) of the three-step overflow pathway to L-phenylalanine. Enterocluster 2 consists of the genera Serratia and Erwinia. Enterocluster 3 includes the genera Cedecea, Kluyvera, Edwardsiella, Hafnia, Yersinia, Proteus, Providencia, and Morganella. Within these three major clusters, a tentative hierarchy of subcluster ordering is formulated on the basis of all data available. This hierarchical framework is proposed as a general working basis for continued refinement of the phylogenetic relationships of enteric bacteria.

Anthranilate Phosphoribosyltransferase↗
PubMed1997

The trp RNA-binding attenuation protein regulates TrpG synthesis by binding to the trpG ribosome binding site of Bacillus subtilis.

The trpG gene of Bacillus subtilis encodes a glutamine amidotransferase subunit which is involved in the biosynthesis of L-tryptophan and folic acid. The trp RNA-binding attenuation protein (TRAP) is involved in controlling expression of trpG at the level of translation in response to changes in the intracellular concentration of tryptophan. We performed in vitro experiments using purified TRAP to elucidate the mechanism of TRAP-dependent trpG regulation. A TRAP-trpG RNA footprint analysis showed that tryptophan-activated TRAP interacts with one UAG, one AAG, and seven GAG repeats present in the trpG transcript. Results from ribosome and TRAP toeprint experiments indicated that the ribosome and TRAP binding sites overlap. Experiments with a B. subtilis cell-free translation system demonstrated that TRAP inhibits TrpG synthesis. Thus, TRAP regulates translation of trpG by blocking ribosome access to the trpG ribosome binding site. Our results are consistent with a model in which each tryptophan-activated TRAP subunit interacts with one trinucleotide repeat in an RNA target, thereby wrapping the transcript around the periphery of the TRAP complex.

Anthranilate Synthase↗