Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “INDOLES”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources
PubMed1975

[Influence of indole-3-alkanecarboxylic acids on glucose utilization in rats].

The influence of various indole-3-alkane-carboxylic acids (indole-3-propionic acid, indole-3-butyric acid and derivatives of this substance) on some parameters of carbohydrate, fat and insulin metabolism were studied in normal and experimentally induced diabetic rats. Earlier it had been shown, by Schillinger and Loge (1973) using rat liver slices for in vitro studies and adrenalectomized rates for in vivo experiments that indole-3-butyric acid and its analogues investigated suppress gluconeogenesis from pyruvate and that these substances have a hypoglycaemic effect when administered orally at doses of 50-250 mg/kg. Indole-3-propionic acid, indole-3-butyric acid, 1-methyl-indole-3-butyric acid, 2-methyl-indole-3-butyric acid and 1-carboxy-6-fluor-1,2,3,4-tetrahydrocarbazol, administered orally at doses up to 1000 mg/kg, had either only a slight or no hypoglycaemic effect at all in intact and streptozotocin-diabetic rats. The suppression of gluconeogenesis observed in vitro thus only has an appreciable effect on blood glucose in vivo when the capacity of the liver to synthetize glucose is reduced. In normal rats indole-3-propionic acid and indole-3-butyric acid led to a deterioration of glucose tolerance following i.v. glucose loading and to a reduction of 14C-U-glucose oxidation. An increase in the concentration of serum free fatty acids (FFA) measured after treatment with indole-3-butyric acid and its 1- and 2-methylated derivatives was not--in accordance with a theory of an interference of the glucose and fatty acid utilization published in literature--considered to be the primary cause since the reduced formation of 14CO2 from radioactive glucose is not normalized when the increased FFA content is reduced by an inhibitor of lipolysis (5-methyl-isoxazol-3-carboxylic acid)...

Animals↗
PubMed1998

Synthesis, properties and biological evaluation of substituted furo[3,2-e] and pyrano[3,2-e]pyrido[4,3-b]indoles.

Furo[3,2-e]- and pyrano[3,2-e]pyrido[4,3-b] indoles were synthesized from 1,4,5-trisubstituted 8-hydroxy-5H-pyrido[4,3-b]indoles. The intermediates, 10-chloro-6H-furo[3,2-e]pyrido[4,3-b]indole (11), 10-chloro-2,6-dihydro-1H-furo[3,2-e]pyrido-[4,3-b]indole (10) and 11-chloro-2,3-dihydro-3H,7H-pyrano[3,2-e]pyrido[4,3-b]indole (15), were substituted by diamines under thermal conditions (180 degrees C). In contrast, 11-chloro-3H,7H-pyrano[3,2-e]pyrido[4,3-b]indole (14), 9-allyl-1-chloro-4,5-dimethyl-5H-pyrido[4,3-b]indole (9a) and 8-propargyloxy-4,5-dimethyl-5H-pyrido[4,3-b]indole (8) led mainly to 1-aminosubstituted 8-hydroxy-5H-pyrido[4,3-b]indole derivatives resulting from an unexpected C3 unit elimination. When examined in three tumour cell lines (L1210 leukaemia, the B16 melanoma and the MCF7 breast adenocarcinoma) the new amino substituted furo[3,2-e]-, dihydrofuro[3,2-e]- and dihydropyrano[3,2-e]-pyrido[4,3-b]indole derivatives revealed cytotoxic properties, especially important for the 2,6-dihydro-1H-furo[3,2-e]pyrido[4,3-b]indole series. The most active compound (12b) significantly inhibits both DNA topoisomerases I and II, and is as potent as Adriamycin at inhibiting cell proliferation and inducing a massive accumulation of L1210 cells in the G2 + M phase of the cell cycle. However, 12b was less active than Adriamycin when tested in vivo against P388 leukaemia or the B16 melanoma tumour models.

Animals↗
PubMed1974

Enzymatic Esterification of Indole-3-acetic Acid to myo-Inositol and Glucose.

Incubation of mature sweet corn kernels of Zea mays in dilute solutions of (14)C-labeled indole-3-acetic acid leads to the formation of (14)C-labeled esters of myo-inositol, glucose, and glucans. Utilizing this knowledge it was found that an enzyme preparation from immature sweet corn kernels of Zea mays catalyzed the CoA- and ATP-dependent esterification of indole-3-acetic acid to myo-inositol and glucose. The esters formed were 2-O-(indole-3-acetyl)-myo-inositol, 1-dl-1-O-(indole-3-acetyl)-myo-inositol, di-O-(indole-3-acetyl)-myo-inositol, tri-O-(indole-3-acetyl)-myo-inositol, 2-O-(indole-3-acetyl)-d-glucopyranose, 4-O-(indole-3-acetyl)-d-glucopyranose and 6-O-(indole-3-acetyl)-d-glycopyranose. An assay system was developed for measuring esterification of (14)C-labeled indole-3-acetic acid by ammonolysis of the esters followed by isolation and counting the radioactive indole-3-acetamide.

Journal Article↗
PubMed2006

Indole rings in palladium(II) complexes. Dual mode of metal binding and aromatic ring stacking causing syn-anti isomerism.

In view of the interesting metal-binding properties of lichen substances and the indole ring as a potential ligand, we studied the Pd(II) complexes of indole-containing ligands, N-(indole-3-ethyl)-Delta(2,11)-enaminousnic acid (IEU) and 4-[2-(indol-3-yl)-ethylamino]pent-3-en-2-one (IEP) obtained by condensation of tryptamine with usnic acid and its model acetylacetone, respectively. Reactions of Pd(II) with IEU and IEP gave isomeric complexes resulting from coordination of the C3 atom of the indole ring in the 3H-indole form, Pd2(IEUH(-2))(2) (1 and 2) and Pd2(IEPH(-2))(2) (3 and 4) (IEUH(-2) and IEPH(-2) denote doubly deprotonated forms of IEU and IEP, respectively). Complexes 1-4 were determined, from the NMR and MS spectra, to have dimeric structures doubly bridged by the indole rings, which were stacked in different orientations. X-ray crystal structure analysis of 3 and 4 established that they are indole-bridged dimers of the [C,N,O]-donor palladacycles with the Pd(II) centers in a square-planar geometry formed by a CN(2)O donor set and are anti and syn isomers with respect to the bridging indole rings, respectively. On the basis of the spectral similarity with 4, 1 and 2 were concluded to be stereoisomers assuming the syn form with the same donor set. The results demonstrate the metal binding and stacking abilities of the indole ring and the stereoisomerism from the sp3 C3 atom formed upon coordination.

Crystallography, X-Ray↗
PubMed1969

Gas chromatographic analysis of acidic indole auxins in Nicotiana.

Acidic indole auxins have been extracted from N. glauca, N. langsdorffii and their 2 tumor-prone 4n- and 2n-hybrids. After purification of the extracts and thin-layer chromatography, acidic indoles were subjected to esterification and gas chromatography. The esters of 4 indole acids were detected and determined: indole-3-acetic acid, indole-3-carboxylic acid, indole-3-propionic acid and indole-3-butyric acid. The indolic nature of fractionated samples was confirmed by spectrophotofluorometry and the physiological significance of the indole esters proven in a biotest. A substantial increase in extractable indole-3-butyric acid in the tumor-prone hybrids suggests an additional pathway of auxin synthesis in these tissues.

Biological Assay↗
PubMed1999

Modulation of drug-metabolising enzyme expression by condensation products of indole-3-ylcarbinol, an inducer in cruciferous vegetables.

Indole-3-ylcarbinol (13C) is formed during processing of cruciferous vegetables and is suggested to be one of the modulators of drug-metabolising enzymes. Indole-3-ylcarbinol is a far less efficient inducer of hepatic enzymes after parenteral than after oral administration, due to formation of active metabolites in the gastrointestinal tract. As indole-3-ylcarbinol is unstable in weakly acidic aqueous solutions, non-active condensation products may be formed from indole-3-ylcarbinol, that cannot be transformed to the active products when reaching the stomach. The purpose of the present study was to test the ability of the condensation products formed at a pH corresponding to that of fresh vegetable juice to modulate the metabolism of xenobiotics. Indole-3-ylcarbinol was incubated in vitro at room temperature in the dark at pH 5.5 and samples taken at various times, for oral administration to rats and for chemical analysis. Indole-3-ylcarbinol was rapidly transformed into various oligomeric products. The 7-ethoxyresorufin O-deethylase activities (marker of cytochrome Cytochrome P450 1A enzymes, CYP1A) in liver, kidney and colon increased with the duration of the in vitro condensation period whereas the formation of 6beta-, 15beta- and and 2alpha-hydroxytestosterone was not affected significantly, indicating no effect on CYP2C11 or CYP3A enzymes. The hepatic metabolism of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). was increased by indole-3-ylcarbinol condensation products and the 4'-OH-PhIP/N-OH-PhIP ratio was decreased due to a significantly increased formation of the proximate genotoxic metabolite. N-OH-PhIP. The activities of DT-diaphorase and glutathione S-transferase were not changed significantly in the rat organs. These experiments clearly indicate that indole-3-ylcarbinol is not the definitive CYP1A inducer and that indole-3-ylcarbinol at near-neutral pH, is transformed to compounds that are inducers by themselves or may be further converted into inducing compounds in the rat stomach. Also, the enzyme inducing potency of indole-3-ylcarbinol containing vegetable juice is apparently enhanced by incubation in vitro before the intake.

Animals↗
PubMed1989

[Indole production in human whole saliva].

It is known that between saliva and oral microorganisms there are close relations. To investigate the salivary factors that influence the metabolism of oral microorganisms, the production and degradation of indole were studied in several salivary supernatants or salivary ultrafiltrates. Washed salivary sediments were mixed with the supernatants or the ultrafiltrates containing tryptophan or indole. After incubation at 37 degrees C for 48 hours, the indole was extracted by petroleum ether and determined spectrophotometrically. The results obtained were as follows: 1) The amount of indole produced in the raw supernatants was generally greater than that produced in the heated supernatants. 2) The production and the degradation of indole in the ultrafiltrates varied according to the saliva samples. 3) Only a small amount of indole was produced when tryptophan was not added to the ultrafiltrates. 4) When the ultrafiltrate was preheated at 98 degrees C, the indole production slightly decreased for only ten minutes. 5) The optimum pH for indole production in the ultrafiltrate was within the range from 7.0 to 8.5 in the presence of 20mM of Good's buffer (MES, MOPS, TAPS). 6) The highest indole production was observed when MOPS (pH7.7) was added at the concentration of 20mM to the ultrafiltrate. 7) The amount of indole production was mainly influenced by salivary sediment, and it was also affected by the ultrafiltrate.

Humans↗
PubMed2002

Characteristics of indolent non-Hodgkin lymphoma in patients with type 1 human immunodeficiency virus infection.

BACKGROUND: There is recent evidence that the incidence of indolent non-Hodgkin lymphoma (NHL) appears to be increased in persons with the acquired immunodeficiency syndrome (AIDS). The current study was conducted to describe the clinical, immunologic, and pathologic characteristics of indolent B-cell lymphoma in patients infected with the human immunodeficiency virus (HIV). METHODS: The current report was a retrospective study of 10 cases of indolent NHL identified from the AIDS-Lymphoma Registry at the University of Southern California School of Medicine. These patients were compared with 336 consecutive patients with systemic intermediate/high-grade AIDS-related NHL who were diagnosed and treated at a single institution. RESULTS: The pathology of the indolent cases included follicular lymphoma (five patients), small lymphocytic lymphoma (two patients), and one case each of mucosa-associated lymphoid tissue (MALT), monocytoid B-cell, and marginal zone lymphoma. When comparing the indolent lymphomas with the intermediate/high-grade AIDS-NHL cases, no differences were observed with regard to demographic characteristics or history of prior opportunistic infection. HIV patients with indolent lymphomas were found to have a significantly higher median CD4+ lymphocyte count compared with patients with intermediate/high-grade NHL (531 /mm3 vs. 90 /mm3) (P < 0.0001). Bone marrow involvement was significantly more common in indolent NHL cases (50%) versus intermediate/high-grade NHL cases (17%) (P = 0.02). The median survival for patients with indolent NHL was significantly longer compared with patients with intermediate/high-grade NHL (66.8 months vs. 7.1 months) (P = 0.007). CONCLUSIONS: Indolent lymphomas occurring in patients infected with HIV appear to differ from intermediate/high-grade lymphomas with regard to immune status and propensity for bone marrow involvement and prolonged survival. The median survival in the group of HIV-seropositive patients with indolent NHL examined in the current study was found to be comparable to that reported in HIV-negative individuals.

Adult↗
PubMed1974

Mechanism of Indole-3-acetic Acid Conjugation: No Induction by Ethylene.

Formation of indole-3-acetic acid-aspartate in detached primary leaves of cowpea (Vigna sinensis Endl.) floating on (14)C-indole-3-acetic acid (3 muc; 3.15 mum, phosphate-citrate buffer, pH 4.75), almost doubled when leaves were pretreated with 31.5 mum(12)C-indole-3-acetic acid for 17 hr and then transferred to (14)C-indole-3-acetic acid for 4 hours as compared with leaves preincubated in buffer only. When leaves were preincubated with ethylene (11.0 and 104 mul/l) instead of (12)C-indole-3-acetic acid, no induction of indole-3-acetylaspartic acid formation was observed, and the rate of indole-3-acetylaspartic acid formation decreased as compared with control leaves. Rhizobitoxine (1.87 mum) inhibited indole-3-acetic acid-induced ethylene production but did not prevent the formation of indole-3-acetylaspartic acid. In view of the similarity of these results and those previously obtained with alpha-naphthaleneacetic acid, it is concluded that ethylene has no role in the auxin-induced indole-3-acetylaspartic acid formation in cowpea leaves.

Journal Article↗
PubMed1988

Characterization of the indole triplet excited state in proteins utilizing laser flash photolysis.

The triplet-triplet absorption spectrum of the sole indole side chain of human serum albumin and its decay kinetics were previously characterized, at room temperature, by using a conventional flash photolysis method [(1978) Proc. Natl. Acad. Sci. USA 75, 1172-1175]. Exploitation of this potentially useful long lived reporter group in protein studies was limited by the excessively large sample size required by that apparatus. The 265 nm laser flash instrument used in the present work avoids this problem at the price of a loss in photo-selectivity. We report that the latter concern can be mitigated. Melittin was studied first because this polypeptide contains a single aromatic residue (W-19), and because its monomeric and tetrameric forms are good models for solvent exposed and buried indole side chains of proteins. For both forms, the indole triplet and neutral radical absorption spectra could be readily time resolved and identified on the basis of shape and differential dioxygen sensitivity. The single tryptophan containing protein human serum albumin was studied next because it contains a large number of other 265 nm absorbing moieties whose transient spectra might complicate the detection of the indole triplet. These transients were shown to not interfere significantly in the wavelength region 450 nm to 600 nm, and, in contrast to the indole triplet, they were relatively dioxygen insensitive. Thus, a facile means is available by which the indole triplet of proteins may be characterized. Subsequently the question of whether this species could be detected in the presence of nuclei acid components was investigated by flashing the phage fd. The putative nucleic acid transients were shown not to interfere and the absorbance of the indole triplet was readily time resolved. The spectral assignment was persuasively confirmed by showing that the indole triplet absorption and phosphorescence emission spectra decay with the same lifetime. The present work thus provides additional evidence for the general applicability of the indole triplet excited state as a long lived intrinsic protein reporter group.

Bacteriophages↗
PubMed1988

Determination of the dioxygen quenching constant for protein and model indole triplets.

The decay of the indole triplet of single tryptophan-containing proteins and model compounds can be readily determined at room temperature in solution by monitoring the triplet absorption or emission following an exciting laser pulse. The dioxygen triplet quenching constants, can be measured for all these molecules and compared to the analogous singlet values determined by fluorescence methods. The dioxygen triplet quenching constant (tkq) ranged from a high of 5.1.10(9) M-1.s-1 for the exposed indole of corticotropin to a low of 0.1.10(9) M-1.s-1 for the buried indole of asparaginase. The ratio of these values with their respective dioxygen singlet quenching constants (skq), tkq/skq, ranged from 0.3 to 0.6 for aqueous exposed polypeptide indoles. For globular proteins the tkq/skq value is observed to be 0.2 +/- 0.1. This lower value for protein indoles is not attributable to 'bulk' environmental or hydrogen bonding effects, since the magnitude of tkq/skq (= 0.5 +/- 0.1) for model indoles was independent of solvent dielectric constant, polarity, and proticity. Temperature-dependence studies were done to test whether tkq could be used to characterize the nature of the protein matrix. The activation energy (Ea) for tkq was found to be 11 +/- 2 kcal/mol for most proteins. This Ea was independent of whether the indole side-chain was solvent exposed or buried in the non-aqueous protein interior. Large Ea values were also obtained for model indoles, naphthalene and nalidixic acid, dissolved in water, whereas the same compounds dissolved in 95% ethanol exhibited much smaller Ea values. These data, in combination with the observation that the tkq of model indoles is insensitive to changes in solvent viscosity, indicate that dioxygen quenching at the triplet level can not be easily used to characterize the dynamics of proteins.

Indoles↗
PubMed2006

Identification of novel short chain 4-substituted indoles as potent alphavbeta3 antagonist using structure-based drug design.

The vitronectin receptor alpha(v)beta(3) has been identified as a promising potential target for the treatment of osteoporosis, diabetic retinopathy and cancer. We have recently reported 5-substituted indoles 3-[5-[2-(5,6,7,8-tetrahydro[1,8]naphthyridin-2-yl)ethoxy]indol-1-yl]-3-(3-pyridyl)propionic acid 3 and 3-[5-[2-(5,6,7,8-tetrahydro[1,8]naphthyridin-2-yl)ethoxy]indol-1-yl]-3-(3,4-methylenedioxyphenyl)propionic acid 4, as an original series of potent alpha(v)beta(3) antagonists with subnanomolar activity. Ligand-protein docking analyses have been performed to generate binding models of three different chemical classes of known alpha(v)beta(3) antagonists with alpha(v)beta(3). Results of this docking study suggested that indoles bearing the basic tetrahydronaphthyridine group at position 4 can easily adopt the correct binding conformation and should be as potent as our current 5-substituted indole leads 3 and 4. This hypothesis was nicely demonstrated by the synthesis of a series of 1,4-disubstituted indoles through a tandem of reactions involving: (i) the N-alkylation of indoles 15 and 22 with propargyl esters and cesium fluoride, and (ii) a Heck coupling reaction between 4-bromoindole and 7-vinyl-3,4-dihydro-2H-[1,8]naphthyridine-1-carboxylic acid tert-butyl ester 12, or (iii) a reductive amination involving the N-substituted-4-aminoindole 23 and the BOC-protected tetrahydro[1,8]naphthyridine aldehyde 13. Among the compounds assayed, 3-(3-pyridyl)-3-[4-[2-(5,6,7,8-tetrahydro[1,8]naphthyridin-2-yl)ethyl]indol-1-yl]propionic acid 21 showed the most promising activity on alpha(v)beta(3) (IC(50)=0.5 nM), and was found to have the same potency as our current leads 3 and 4, while maintaining selectivity over alpha(IIb)beta(IIIa). Moreover, based on the reasonable apparent permeability coefficient in an in vitro CACO-2 cell monolayer assay (P(app) apical/basolateral=2.2 x 10(-6)cm/s, P(app) basolateral/apical=2.5 x 10(-6)cm/s), compound 21 is expected to be absorbed through the intestine in human. Thus, 1,4-disubstituted indole 21 represents a new lead for this novel class of conformationally restricted alpha(v)beta(3) antagonists. Additionally, this study validates the pharmacophore model previously postulated and provides an improved basis for further structure-based drug design in the field of alpha(v)beta(3).

Drug Design↗
PubMed2002

Chemical defenses of crucifers: elicitation and metabolism of phytoalexins and indole-3-acetonitrile in brown mustard and turnip.

The metabolism of the cruciferous phytoalexins brassinin and cyclobrassinin, and the related compounds indole-3-carboxaldehyde, glucobrassicin, and indole-3-acetaldoxime was investigated in various plant tissues of Brassica juncea and B. rapa. Metabolic studies with brassinin showed that stems of B. juncea metabolized radiolabeled brassinin to indole-3-acetic acid, via indole-3-carboxaldehyde, a detoxification pathway similar to that followed by the "blackleg" fungus (Phoma lingam/Leptosphaeria maculans). In addition, it was established that tetradeuterated brassinin was incorporated into the phytoalexin brassilexin in B. juncea and B. rapa. On the other hand, the tetradeuterated indole glucosinolate glucobrassicin was not incorporated into brassinin, although the chemical structures of brassinins and indole glucosinolates suggest an interconnected biogenesis. Importantly, tetradeuterated indole-3-acetaldoxime was an efficient precursor of phytoalexins brassinin, brassilexin, and spirobrassinin. Elicitation experiments in tissues of Brassica juncea and B. rapa showed that indole-3-acetonitrile was an inducible metabolite produced in leaves and stems of B. juncea but not in B. rapa. Indole-3-acetonitrile displayed antifungal activity similar to that of brassilexin, was metabolized by the blackleg fungus at slower rates than brassinin, cyclobrassinin, or brassilexin, and appeared to be involved in defense responses of B. juncea.

Anti-Infective Agents↗
PubMed1986

Production and degradation of indole by gram-negative bacteria.

The indole reaction is performed in various modifications with regard both to the reagents and to the media used. Especially the medium has hitherto attracted little attention and there are divergent recommendations for its composition. The comparison of some broths without and with addition of tryptophan after incubation with different indole-positive species revealed that tryptone without tryptophan yielded stronger reactions than with tryptophan added. Other broths showed stronger reactions with tryptophan. Investigations revealed that numerous indole-positive as well as indole-negative species possess an enzyme system degrading indole. It is induced after one or two days of incubation and acts slowly. All species of the Morganella-Proteus-Providencia group possess it, as does Serratia. Some other species show different characteristics. The production of indole from peptone containing tryptophan and the degradation of indole by such species of bacteria are due to figures showing one or more peaks depending on time. Any false indole reactions described up to now may also be explained by the antagonism of the two enzyme systems. Therefore, the indole reaction should be standardized with regard to the medium used to avoid some of these difficulties.

Culture Media↗
PubMed1998

Preliminary results of the use of indole-3-carbinol for recurrent respiratory papillomatosis.

OBJECTIVE: We report the preliminary results of a phase I trial using indole-3-carbinol for the treatment of recurrent respiratory papillomatosis. Indole-3-carbinol is a chemical that is found in high concentrations in cruciferous vegetables and has been shown to alter the growth pattern of recurrent respiratory papillomatosis cell cultures and to be effective in an in vivo animal model of recurrent respiratory papillomatosis. METHODS: Eighteen patients were treated with oral indole-3-carbinol and had a minimum follow-up of 8 months and a mean follow-up of 14.6 months. All patients received indole-3-carbinol, and outcome measures included a change in papilloma growth rate and the need for surgery during treatment compared with before treatment. All patients had serial examinations with videoendoscopy to document papilloma location and growth rate. RESULTS: Thirty-three percent (6 of 18) of the study patients had a cessation of their papilloma growth and have not required surgery since the start of the study. Six patients have had reduced papilloma growth rate, and 6 (33%) patients have shown no clinical response to indole-3-carbinol. Indole-3-carbinol affects the ratio of hydroxylation of estradiol; changes in the ratios of urinary 2-hydroxylation and 16-hydroxylation of estradiol caused by indole-3-carbinol correlated well with clinical response. No major complications or changes in the children's growth curve were noted. CONCLUSIONS: The preliminary results of treating recurrent respiratory papillomatosis with indole-3-carbinol holds promise. Longer follow-up of this patient group and a blinded, controlled trial are required. We conclude that indole-3-carbinol appears to be safe and well tolerated and may be an efficacious treatment for recurrent respiratory papillomatosis.

Adult↗
PubMed1990

The tryptophan synthase bienzyme complex transfers indole between the alpha- and beta-sites via a 25-30 A long tunnel.

The bacterial tryptophan synthase bienzyme complexes (with subunit composition alpha 2 beta 2) catalyze the last two steps in the biosynthesis of L-tryptophan. For L-tryptophan synthesis, indole, the common metabolite, must be transferred by some mechanism from the alpha-catalytic site to the beta-catalytic site. The X-ray structure of the Salmonella typhimurium tryptophan synthase shows the catalytic sites of each alpha-beta subunit pair are connected by a 25-30 A long tunnel [Hyde, C. C., Ahmed, S. A., Padlan, E. A., Miles, E. W., & Davies, D. R. (1988) J. Biol. Chem. 263, 17857-17871]. Since the S. typhimurium and Escherichia coli enzymes have nearly identical sequences, the E. coli enzyme must have a similar tunnel. Herein, rapid kinetic studies in combination with chemical probes that signal the bond formation step between indole (or nucleophilic indole analogues) and the alpha-aminoacrylate Schiff base intermediate, E(A-A), bound to the beta-site are used to investigate tunnel function in the E. coli enzyme. If the tunnel is the physical conduit for the transfer of indole from the alpha-site to the beta-site, then ligands that block the tunnel should also inhibit the rate at which indole and indole analogues from external solution react with E(A-A). We have found that when D,L-alpha-glycerol 3-phosphate (GP) is bound to the alpha-site, the rate of reaction of indole and nucleophilic indole analogues with E(A-A) is strongly inhibited. These compounds appear to gain access to the beta-site via the alpha-site and the tunnel, and this access is blocked by the binding of GP to the alpha-site. However, when small nucleophiles such as hydroxylamine, hydrazine, or N-methylhydroxylamine are substituted for indole, the rate of quinonoid formation is only slightly affected by the binding of GP. Furthermore, the reactions of L-serine and L-tryptophan with alpha 2 beta 2 show only small rate effects due to the binding of GP. From these experiments, we draw the following conclusions: (1) L-Serine and L-tryptophan gain access to the beta-site of alpha 2 beta 2 directly from solution. (2) The small effects of GP on the rates of the L-serine and L-tryptophan reactions are due to GP-mediated allosteric interactions between the alpha- and beta-sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Allosteric Regulation↗
PubMed1992

Selective, centrally acting serotonin 5-HT2 antagonists. 2. Substituted 3-(4-fluorophenyl)-1H-indoles.

A series of 3-(4-fluorophenyl)-1H-indoles substituted in the 1-position with 4-piperidinyl, 1,2,3,6-tetrahydro-4-pyridinyl, and 4-piperazinyl was synthesized. By variation of the substituents in the benzene part of the indole nucleus in 1-[2-[4-[3-4-fluorophenyl)-1H-indol-1-yl]-1-piperidinyl]-ethyl]-2- imidazolidinones, the highest 5-HT2 receptor affinity and selectivity with respect to dopamine D2 receptors and alpha 1 adrenoceptors were obtained by 5-methyl substitution. Different substituents were introduced in the 1-position of the piperidine ring in the 5-methyl-substituted derivative. Thus replacement of the 2-(2-imidazolidinon-1-yl)ethyl side chain with a 2-(1,3-dimethyl-1-ureido)ethyl or methyl substituent resulted in unchanged affinity and selectivity for 5-HT2 receptors. Replacement with a 2-[3-(2-propyl)-2-imidazolidinon-1-yl]ethyl side chain reduced binding to alpha 1 adrenoceptors with a factor of four, while affinities for 5-HT2 and D2 receptors were retained, compared to the 3-unsubstituted imidazolidinone. Indoles substituted in the 1-position with 4-piperazinyl had generally weaker affinity for both 5-HT2 and D2 receptors compared to corresponding 4-piperidinyl- and 1,2,3,6-tetrahydro-4-pyridinyl-substituted indoles. Introduction of a methyl group in the 2-position of the 5-methyl-substituted indole resulted in further increase of selectivity for the 5-HT2 receptor. Compounds with potent receptor binding also potently inhibited the quipazine-induced head twitch syndrome in rats. The compounds were equally active after oral and subcutaneous administration and showed a long duration of action (> 24 h). In general, the derivatives were found to be considerably more potent at 24 h than at 2 h after the administration. The compounds within this series were prepared as analogues of the previously described 1-(4-fluorophenyl)-3-(4-piperidyl)-1H-indoles by interchange of the C-3 carbon atom and the nitrogen atom in the indole nucleus. The pharmacological results indicate that this isosteric replacement results in higher selectivity for 5-HT2 receptors compared to the former series. The 1-[2-[4-[2,5-dimethyl-3-(4-fluorophenyl)-1H-indol-1-yl]-1- piperidinyl]ethyl]-2-imidazolidinone has high affinity for 5-HT2 receptors (IC50 = 3.4 nM) and extremely low affinity for both dopamine D2 receptors (IC50 = 6900 nM) and alpha 1 adrenoceptors (IC50 = 2300 nM).

Animals↗
PubMed1989

Synthesis and evaluation of N,N-di-n-propyltetrahydrobenz[f]indol-7-amine and related congeners as dopaminergic agonists.

An evaluation of 6-[2-(di-n-propylamino)ethyl]indole (4), its rigid analogue N,N-di-n-propyl-5,6,7,8-tetrahydrobenz[f]indol-7-amine (5), and some related congeners, for ability to suppress serum prolactin in reserpinized rats, revealed modest biological activity in this in vivo model of dopaminergic activity. Although the indole N-H in these compounds can be considered to be oriented "meta" with respect to the ethylamine side chain, compounds with the indole N-H located in the other "meta" position (i.e. 4-[2-(di-n-propylamino)ethyl]indole (2) or its rigid benz[e]indole analogue 3) were much more potent dopamine agonists. The results argue for a particular orientation of the indole N-H vector. In addition, relatively potent dopamine agonists also resulted when the pyrrole portion of the indole ring was replaced by a methanesulfonamido function, supporting the idea that the indole N-H serves as a hydrogen-bond donor.

Animals↗