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PubMed1981

The effect of short-term total parenteral nutrition on hepatic function in the human neonate: a prospective randomized study demonstrating alteration of hepatic canalicular function.

Twenty-one infants who were candidates for TPN because of respiratory disease were randomized into experimental (TPN) and control (glucose-electrolyte) groups. Serum GOT, GPT, GGTP, 5' nucleotidase, total, direct, and conjugated (ethyl anthranilate-reactive) bilirubin, and bile salt concentrations were determined at entry into the study and at one week. One week of TPN caused significant elevations of GGTP, 5'-N and EA bilirubin values, whereas SGOT, SGPT, SBS, and total and direct bilirubin were unaffected. Addition of a lipid infusion to TPN did not alter these differences. These data are interpreted as showing: (1) amino acid infusion has an early effect on hepatic function which is independent of the many diseases for which this therapy is used and of the concomitant use of lipid; (2) the initial effect appears to be on the canalicular membrane; and (3) the sinusoidal membrane is apparently unaffected by one week of TPN.

Amino Acids↗
PubMed1973

Genetic studies relating to the production of transformed clones diploid in the tryptophan region of the Bacillus subtilis genome.

Transformation experiments with Bacillus subtilis strains carrying trpE26 (the marker responsible for the detection of merodiploid clones after transformation or transduction) have established the precise position of this marker on the "aromatic region" of the chromosome, at the distal end of the anthranilate synthetase locus. Integration efficiency of the mutant allele (trpE26) seems to be very low. Co-transfer of markers situated on either side of it is almost nil when both donor and recipient carry this mutation. The "exclusion" of trpE26 does not, however, affect recombination frequencies for nearby markers. To explain these facts we considered the hypothesis of a preferential breakage of the deoxyribonucleic acid (DNA) at the trpE26 site or that of an insertion mutation. These studies have also demonstrated the establishment of physical linkage of a marker from the exogenote (hisH2) to a resident marker (tyrA1) in stable and unstable merodiploid clones, thus confirming integration of the donor DNA segment into a genetic structure of the recipient. Furthermore, duplication was shown in merodiploid clones (through reversion and transformation) for a locus of the recipient (tyrA) which was not involved in the initial transformation. This suggests that the diploid condition in this region extends beyond the transformed area. Interpretation of the genetic constitution of these partial diploids calls for postulation of the existence of long duplications, a second (incomplete) chromosome, or an episome-like element.

Alleles↗
PubMed2002

Indole-3-acetic acid metabolism in Lemna gibba undergoes dynamic changes in response to growth temperature.

Auxin is the mobile signal controlling the rate of growth and specific aspects of the development of plants. It has been known for over a century that auxins act as the messenger linking plant development to specific environmental changes. An often overlooked aspect of how this is accomplished is the effect of the environment on metabolism of the major plant auxin, indole-3-acetic acid (IAA). We have studied the metabolism of IAA in relation to one environmental variable, growth temperature. The model system used was an inbred line of the aquatic monocot Lemna gibba G-3, 3F7-11 grown at temperatures ranging from 5 degrees C to 35 degrees C. IAA levels, the rate of IAA turnover, and the patterns of label incorporation from IAA precursors were measured using stable isotope-mass spectrometric techniques and were evaluated relative to growth at the experimental temperatures. IAA levels exhibited unusually high variability in plants grown at 15 degrees C and 20 degrees C. Turnover rates were quite rapid throughout the range of experimental temperatures except at 25 degrees C, where IAA turnover was notably slower. These results suggest that a transition occurred over these temperatures for some aspect of IAA metabolism. Analysis of [(15)N]anthranilate and [(2)H(5)]tryptophan (Trp) incorporation into IAA showed that Trp-dependent biosynthesis predominated at 15 degrees C; however, Trp-independent biosynthesis of IAA was the major route to IAA at 30 degrees C. The effects of growth temperature on auxin levels have been reported previously, but no prior studies correlated these effects with which pathway becomes the primary one for IAA production.

Carbon Radioisotopes↗
PubMed1996

Re-evaluation of chromosomal aberration induction on nine mouse lymphoma assay "unique positive' NTP carcinogens.

In a collaborative study organized under the JEMS MMS, nine mouse lymphoma assay (MLA) "unique positive' NTP rodent carcinogens were re-evaluated by an in vitro chromosomal aberration assay using Chinese hamster lung fibroblast cells (CHL/IU). Six of nine chemicals induced chromosomal aberrations; bromodichloromethane, chlorendic acid and isophorone induced structural aberrations, and chlorodibromomethane, pentachloroethane and 1,1,1,2-tetrachloroethane induced numerical aberrations (polyploidy). These six chemicals, therefore, are not uniquely positive in the MLA. The difference between the NTP results and ours might be due to the use of different cell lines and protocols, and in some cases, to different interpretations of polyploidy. The remaining three chemicals, benzyl acetate, cinnamyl anthranilate and trichloroethylene, were negative in this study.

Animals↗
PubMed1992

Cloning the Cryptococcus neoformans TRP1 gene by complementation in Saccharomyces cerevisiae.

We have cloned the phosphoribosyl anthranilate isomerase (PRAI)-encoding gene (TRP1) of Cryptococcus neoformans by genetic complementation in Saccharomyces cerevisiae. Sequence analysis of this gene revealed it to be 939 bp in length, and without known promoter or termination sequences. Unlike some of the filamentous fungi, where PRAI enzymatic activity is controlled by a trifunctional gene product, the C. neoformans PRAI appears to be unifunctional. PRAI of C. neoformans exhibits 39% amino acid (aa) sequence identity compared to the S. cerevisiae counterpart. The TRP1 gene of C. neoformans maps to different size chromosomes in strains with different serotypes. The cloning of this gene for vector constructions, and the demonstration that S. cerevisiae can be used as a surrogate for C. neoformans gene expression, should help with the molecular studies of this significant fungal pathogen in our increasing immunocompromised population.

Aldose-Ketose Isomerases↗
PubMed1994

Directed mutagenesis of a regulatory palindromic sequence upstream from the Brevibacterium lactofermentum tryptophan operon.

A cloned 9.6-kb fragment of Brevibacterium lactofermentum DNA, carrying the entire trp operon and upstream regulatory sequences, produces a polycistronic 7.0-kb transcript as detected by hybridization with an internal probe. The transcription start point (tsp) was identified by S1 mapping. The operator-promoter (OP) region subcloned in Escherichia coli and B. lactofermentum promoter-probe vectors exhibited about tenfold higher activity in B. lactofermentum. A 14-bp wild-type (wt) palindrome located at bp -15 to -28 was mutated to change the conserved adenine adjacent to the axis of symmetry. The wt and mutated OP regions were coupled to the amy reporter gene (encoding alpha-amylase [Amy]) or to the 5' region (trpE and trpG genes) of the trp operon, for expression studies. Constructions with the regulatory signals coupled to the wt trpE-trpG genes were introduced in a B. lactofermentum trpE mutant (obtained by gene disruption). The mutation in the palindrome did not affect the promoter activity in B. lactofermentum or E. coli when grown in minimal medium. Tryptophan repressed the OP as assayed by the anthranilate synthase (AS) activity in B. lactofermentum in constructions with the wt OP region, but surprisingly, caused a large stimulation of either AS or the Amy reporter activity, in constructions with the mutated OP. The palindromic sequence is, therefore, involved in a dual repression-stimulation control of expression of the trp operon.

Anthranilate Synthase↗
PubMed1997

Comparison of the effects of cinnamyl anthranilate on hepatic peroxisome proliferation and cell replication in the rat and mouse.

The effects of cinnamyl anthranilate (CA) have been compared in female B6C3F1 mice and female F344 rats fed diets containing 0-3.0% CA for periods of 1, 4, and 13 weeks. In the mouse, treatment with CA at all time points produced a marked dose-dependent increase in relative liver weight and hepatic peroxisome proliferation as demonstrated by the induction of peroxisomal (cyanide-insensitive palmitoyl-CoA oxidation) and microsomal (lauric acid 12-hydroxylase) fatty acid oxidizing enzyme activities. CA produced only small increases in relative liver weight and palmitoyl-CoA oxidation in the rat and did not induce lauric acid 12-hydroxylase activity. Replicative DNA synthesis was studied by implanting osmotic pumps containing 5-bromo-2'-deoxyuridine during Study Weeks 0-1, 3-4, and 12-13. After 1 week of CA treatment, labeling index values were increased in rat and to a greater extent in mouse hepatocytes. While CA treatment for 4 and 13 weeks did not increase hepatocyte-labeling index values in the rat, a sustained stimulation of replicative DNA synthesis was observed at some dietary levels in the mouse. These results demonstrate a marked species difference between the hepatic effects of CA in female B6C3F1 mice and female F344 rats. While CA is a potent peroxisome proliferator in the mouse, it is only a very weak agent in the rat. The formation of liver tumors in long-term studies, at high doses of CA, appears to be attributable to a sustained stimulation of both peroxisome proliferation and cell replication in mouse hepatocytes.

Animals↗
PubMed2004

Tryptophan recycling is responsible for the interferon-gamma resistance of Chlamydia psittaci GPIC in indoleamine dioxygenase-expressing host cells.

Comparative genomics indicates that vast differences in Chlamydia sp. host range and disease characteristics can be traced back to subtle variations in gene content within a region of the chromosome termed the plasticity zone. Genes required for tryptophan biosynthesis are located in the plasticity zone; however, the complement of genes encoded varies depending on the chlamydial species examined. Of the sequenced chlamydia genomes, Chlamydia psittaci GPIC contains the most complete tryptophan biosynthesis operon, encoding trpRDCFBA. Immediately downstream of the trp operon are genes encoding kynureninase and ribose phosphate pyrophosphokinase. Here, we show that, in GPIC, these genes are transcribed as a single transcript, the expression of which is regulated by tryptophan. Complementation analyses, using various mutant Escherichia coli isolates, indicate that the tryptophan biosynthesis, kynureninase and ribose phosphate pyrophosphokinase gene products are functional. Furthermore, growth of C. psittaci GPIC in HeLa cells, cultured in tryptophan-free medium, could be rescued by the addition of anthranilate, kynurenine or indole. In total, our results indicate that this complement of genes enables GPIC to recycle tryptophan and thus accounts for the interferon-gamma resistant phenotype displayed in indoleamine-2,3-dioxygenase-expressing host cells.

Amino Acid Sequence↗
PubMed1977

Media dependence of commitment in Bacillus subtilis.

At some time during sporulation development, cells of Bacillus subtilis develop a commitment to continue sporulation even after addition of or dilution into a fresh nutrient. The extent of commitment was measured by the titer of spores produced at the time at which the original culture sporulated maximally. Since newly formed spores of B. subtilis soon germinate in the replenished medium, the measurement of their titer, especially of heat-resistant spores, gave low values. This problem was avoided by the germination-delaying effect of methyl anthranilate (1 mM) when added together with the fresh nutrients. In a given culture, the titer of committed cells was then independent of the method by which it was measured, i.e., by the phase-bright, octanol-resistant, or heat-resistant spore titer. The time of commitment depended on the type of nutrient added. Commitment occurred earlor casein hydrolysate. The rates at which non-metabolizable amino acid analogues or the 14C from an amino acid mixture were taken up by the cells increased toward the end of growth and later declined. This decline occurred slowly and was only weakly correlated with the commitment time of an analogous amino acid.

Amino Acids↗
PubMed1977

Neurospora crassa glutamine synthetase. Translation of specific messenger ribonucleic acid in a cell-free system derived from rabbit reticulocytes.

The total reticulocyte lysate cell-free protein-synthesizing system was incubated in the presence of Neurospora crassa RNA. With the aid of an antibody directed against purified N. crassa glutamine synthetase, the synthesis of a specific protein was detected. This protein precipitates with antiglutamine synthetase using both direct and indirect procedures, migrates with the same molecular weight as the monomer of N. crassa glutamine synthetase when subjected to acrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, and chromatographs as N. crassa glutamine synthetase on anthranilate-bound Sepharose. These data indicate the translation of the mRNA that codes for N. crassa glutamine synthetase. This RNA behaves as poly(A)-containing material when fractionated on oly(U)-Sepha-rose.

Animals↗
PubMed1997

Solution structure of the esperamicin A1-DNA complex.

Esperamicin A1 is an enediyne antibiotic possessing antitumor activity associated with its ability to bind and, following activation, affect strand cleavage of DNA. We report on the solution structure of the esperamicin A1-d(C-G-G-A-T-C-C-G) duplex complex based on a combined analysis of NMR and molecular dynamics calculations including intensity refinement in a water box. The refined solution structures of the complex provide a molecular explanation of the sequence specificity for binding and cleavage by this member of the enediyne family of antitumor antibiotics. Esperamicin A1 binds to the DNA minor groove with its methoxyacrylyl-anthranilate moiety intercalating into the helix at the (G2-G3)-(C6'-C7') step. The methoxyacrylyl-anthranilate intercalator and the minor groove binding A-B-C+ risaccharide moieties rigidly anchor the enediyne in the minor groove such that the pro-radical centers of the enediyne are proximal to their anticipated proton abstraction sites. Specifically, the pro-radical C-3 and C-6 atoms are aligned opposite the abstractable H-5' (pro-S) proton of C6 and the H-1' proton of C6' on partner strands, respectively, in the complex. The thiomethyl sugar B residue is buried deep in an edgewise manner in the minor groove with its two faces sandwiched between the walls of the groove. Further, the polarizable sulfur atom of the thiomethyl group of sugar B residue is positioned opposite and can hydrogen-bond to the exposed amino proton of G3' in the complex. There is little perturbation away from a right-handed Watson-Crick base-paired duplex in the complex other than unwinding of the helix at the intercalation site and widening of the minor groove centered about the enediyne-binding and anthranilate intercalation sites. Sequence-specific binding of esperamicin A1 to the d(C-G-G-A-T-C-C-G) duplex is favored by the complementarity of the fit between the drug and the floor of the minor groove, good stacking between the intercalating anthranilate ring and flanking purine bases and intermolecular hydrogen-bonding interactions.

Aminoglycosides↗
PubMed1995

Indoleglycerol phosphate synthase-phosphoribosyl anthranilate isomerase: comparison of the bifunctional enzyme from Escherichia coli with engineered monofunctional domains.

Putative domain--domain interactions of the monomeric bifunctional enzyme indoleglycerol phosphate synthase:phosphoribosyl anthranilate isomerase from Escherichia coli were probed by separating the domains on the gene level and expressing them as monofunctional proteins. The engineered monofunctional enzymes were found to be stable, monomeric proteins with virtually full catalytic activity. In addition, binding of indolyglycerol phosphate to the active site of indoleglycerol phosphate synthase and binding of reduced 1-[(2-carboxyphenyl)amino]-1-deoxyribulose 5-phosphate, a competitive inhibitor of both indoleglycerol phosphate synthase and phosphoribosyl anthranilate isomerase, were almost identical in both the mono- and bifunctional enzymes. Furthermore, no association between the monofunctional enzymes was found, neither in vitro, by sedimentation and gel filtration experiments, nor in vivo, by coexpression of the domains in the same cell. Thus, no selective advantages of the bifunctional enzyme from Escherichia coli over the respective monofunctional enzymes were found on a functional level. However, the phosphoribosyl anthranilate isomerase domain appears to stabilize the indoleglycerol phosphate synthase domain of the bifunctional enzyme from Escherichia coli by interactions that seem to subtly influence the kinetics of ligand binding.

Aldose-Ketose Isomerases↗
PubMed1978

Tryptophan biosynthesis in Saccharomyces cerevisiae: control of the flux through the pathway.

Enzyme derepression and feedback inhibition of the first enzyme are the regulatory mechanisms demonstrated for the tryptophan pathway in Saccharomyces cerevisiae. The relative contributions of the two mechanisms to the control of the flux through the pathway in vivo were analyzed by (i) measuring feedback inhibition of anthranilate synthase in vivo, (ii) determining the effect of regulatory mutations on the level of the tryptophan pool and the flux through the pathway, and (iii) varying the gene dose of individual enzymes of the pathway at the tetraploid level. We conclude that the flux through the pathway is adjusted to the rate of protein synthesis by means of feedback inhibition of the first enzyme by the end product, tryptophan. The synthesis of the tryptophan enzymes could not be repressed below a basal level by tryptophan supplementation of the media. The enzymes are present in excess. Increasing or lowering the concentration of individual enzymes had no noticeable influencing on the overall flux to tryptophan. The uninhibited capacity of the pathway could be observed both upon relieving feedback inhibition by tryptophan limitation and in feedback-insensitive mutants. It exceeded the rate of consumption of the amino acid on minimal medium by a factor of three. Tryptophan limitation caused derepression of four of the five tryptophan enzymes and, as a consequence, led to a further increase in the capacity of the pathway. However, because of the large reserve capacity of the "repressed" pathway, tryptophan limitation could not be imposed on wild-type cells without resorting to the use of analogs. Our results, therefore, suggest that derepression does not serve as an instrument for the specific regulation of the flux through the tryptophan pathway.

Anthranilate Synthase↗
PubMed1983

Detection of bilirubin conjugates in faeces of germfree rats.

The presence of bilirubin conjugates in faeces from germfree (GF) and conventional (CONV) rats was tested after using affinity chromatography and Porapak Q chromatography as clean-up procedures. The bilirubin conjugates were detected as their ethyl anthranilate azopigments after separation by thin layer chromatography (tlc). Azopigments prepared from bile of GF and CONV rats served as a reference material for the tlc analysis. After tlc of the faecal azopigment preparations it was concluded that GF rat faeces contains bilirubin conjugates, while faeces from CONV rats is devoid of conjugated bilirubin. The findings suggest that the main bilirubin conjugates present in faeces from GF rats are of the glucuronic acid type.

Animals↗
PubMed2005

Role of the N-terminal extension of the (betaalpha)8-barrel enzyme indole-3-glycerol phosphate synthase for its fold, stability, and catalytic activity.

Indole-3-glycerol phosphate synthase (IGPS) catalyzes the fifth step in the biosynthesis of tryptophan. It belongs to the large and versatile family of (betaalpha)(8)-barrel enzymes but has an unusual N-terminal extension of about 40 residues. Limited proteolysis with trypsin of IGPS from both Sulfolobus solfataricus (sIGPS) and Thermotoga maritima (tIGPS) removes about 25 N-terminal residues and one of the two extra helices contained therein. To assess the role of the extension, the N-terminally truncated variants sIGPSDelta(1-26) and tIGPSDelta(1-25) were produced recombinantly in Escherichia coli, purified, and characterized in comparison to the wild-type enzymes. Both sIGPSDelta(1-26) and tIGPSDelta(1-25) have unchanged oligomerization states and turnover numbers. In contrast, their Michaelis constants for the substrate 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate are increased, and their resistance toward unfolding induced by heat and guanidinium chloride is decreased. sIGPSDelta(1-26) was crystallized, and its X-ray structure was solved at 2.8 A resolution. The comparison with the known structure of sIGPS reveals small differences that account for its reduced substrate affinity and protein stability. The structure of the core of sIGPSDelta(1-26) is, however, unchanged compared to sIGPS, explaining its retained catalytic activity and consistent with the idea that it evolved from the same ancestor as the phosphoribosyl anthranilate isomerase and the alpha-subunit of tryptophan synthase. These (betaalpha)(8)-barrel enzymes catalyze the reactions preceding and following IGPS in tryptophan biosynthesis but lack an N-terminal extension.

Amino Acid Sequence↗
PubMed1970

Mechanism of 3-methylanthranilic acid derepression of the tryptophan operon in Escherichia coli.

3-Methylanthranilic acid (3MA) inhibits growth and causes derepression of the tryptophan biosynthetic enzymes in wild-type strains of Escherichia coli. Previous reports attributed this effect to an inhibition of the conversion of 1-(o-carboxyphenylamino)-1-deoxyribulose 5-phosphate to indole-3-glycerol phosphate and a consequent reduction in the concentration of endogenous tryptophan. Our studies have shown that 3MA-resistant mutants linked to the tryptophan operon have a feedback-resistant anthranilate synthetase; mutants with an altered indole-3-glycerol phosphate synthetase were not found. 3MA or 7-methylindole can be metabolized to 7-methyltryptophan, and 3MA, 7-methylindole, and 7-methyltryptophan lead to derepression of the tryptophan operon. Furthermore, 3MA-resistant mutants are also resistant to 7-methylindole derepression. These results strongly suggest that the primary cause of derepression by 3MA is through its conversion to 7-methyltryptophan, which can inhibit anthranilate synthetase, thereby decreasing the concentration of endogenous tryptophan. Unlike 5- or 6-methyltryptophan, 7-methyltryptophan does not appear to function as an active corepressor.

Culture Media↗
PubMed1971

Excretion in dog bile of glucose and xylose conjugates of bilirubin.

1. T.l.c. with neutral solvent systems of ethyl anthranilate azopigments derived from bile of man, dog and rat revealed pronounced species variation. The less polar components (alpha-group) could be separated conveniently by development with chloroform-methanol (17:3, v/v). 2. The azopigment material derived from gallbladder bile of dog contained about 10% of azobilirubin beta-d-monoxyloside (azopigment alpha(2)) and 30% of azobilirubin beta-d-monoglucoside (azopigment alpha(3)). The sugar moieties were identified by t.l.c. with acidic, neutral and basic solvent systems and by anion-exchange column chromatography of their boric acid complexes. Treatment of the purified azopigments with ammonia vapour led to the formation of the amide of azobilirubin, indicating that both pigments are ester glycosides. The beta-d configuration was demonstrated by enzymic studies with emulsin (an adequate source of beta-glucosidase activity) and with Mylase-P (an adequate source of beta-glucosidase and beta-xylosidase activities). 3. Hydrolysis studies with model substrates and with the alpha(2)- and alpha(3)-azopigments suggested that in Mylase-P the beta-glucosidase and beta-xylosidase activities reside in separate enzymes. 4. Compared with the accepted conjugation with glucuronic acid as a major route of detoxication in mammals, the detection of large amounts of xylose and glucose conjugates of bilirubin in dog bile suggests that the underlying biosynthetic pathways may be important alternative routes of detoxication.

Ammonia↗