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1.
Chemistry ; 30(27): e202400681, 2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38417144

RESUMO

The bulky ß-diketiminate ligand frameworks [BDIDCHP]- and [BDIDipp/Ar]- (BDI=[HC{C(Me)2N-Dipp/Ar}2]- (Dipp=2,6-diisopropylphenyl (Dipp); Ar=2,6-dicyclohexylphyenyl (DCHP) or 2,4,6-tricyclohexylphyenyl (TCHP)) have been developed for the kinetic stabilisation of the first europium (II) hydride complexes, [(BDIDCHP)Eu(µ-H)]2, [(BDIDipp/DCHP)Eu(µ-H)]2 and [(BDIDipp/TCHP)Eu(µ-H)]2, respectively. These complexes represent the first step beyond the current lanthanide(II) hydrides that are all based on ytterbium. Tuning the steric profile of ß-diketiminate ligands from a symmetrical to unsymmetrical disposition, enhanced solubility and stability in the solution-state. This provides the first opportunity to study the structure and bonding of these novel Eu(II) hydride complexes crystallographically, spectroscopically and computationally, with their preliminary reactivity investigated.

2.
J Org Chem ; 89(16): 11631-11640, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-39081027

RESUMO

α-Azido ketones and their vinylogous relatives ß-alkoxy-γ-azido enones are versatile building blocks for constructing diverse heterocyclic products, but are prone to azide decomposition. Here, we report their condensation with propargylic amines and investigate the fate of the intermediate azido-enamine condensation products, both experimentally and theoretically. Efficient intramolecular cycloaddition was observed for electron-poor azide substrates, and a range of diversely substituted [1,2,3]triazolo[1,5-a]pyrazine products is reported. For electron-rich substrates, azide decomposition predominated. Computational modeling of possible pathways from the azido-enamine intermediates revealed two alternative mechanisms for azide decomposition, which were consistent with observed side products.

3.
Org Biomol Chem ; 20(17): 3511-3527, 2022 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-35230376

RESUMO

In the quest for new modulators of the Farnesoid-X (FXR) and Takeda G-protein-coupled (TGR5) receptors, bile acids are a popular candidate for drug development. Recently, bile acids endowed with a C16-hydroxy group emerged as ligands of FXR and TGR5 with remarkable agonistic efficacies. Inspired by these findings, we synthesised a series of C16-hydroxylated 12ß-methyl-18-nor-bile acid analogues from a Δ13(17)-12ß-methyl-18-nor-chenodeoxycholic acid intermediate (16), the synthesis of which we reported previously. The preparation of these aptly named 12ß-methyl-18-nor-avicholic acids (17, 18, 41 and 42) was accomplished via allylic oxidation at C16, hydrogenation of the C13→C17 double bond and selective reduction of the C16-carbonyl group. Described also are various side products which were isolated during the evaluation of methods to affect the initial allylic oxidation. In addition, C23-methyl modified 12ß-methyl-18-nor-bile acids with (48, 49, 51 and 52) and without a C16-hydroxy group (45, 46 and 55), were synthesized to enable comparison of biological activities between these compounds and their un-methylated counterparts. As a result of our investigations we identified (23R)-12ß,23-dimethyl-18-nor-chenodeoxycholic acid (46) and 12ß-methyl-17-epi-18-nor-chenodeoxycholic acid 53 as TGR5 ligands with EC50 values of 25 µM.


Assuntos
Ácidos e Sais Biliares , Ácido Quenodesoxicólico , Ácidos e Sais Biliares/farmacologia , Ácido Quenodesoxicólico/análogos & derivados , Hidrogenação , Ligantes
4.
Arch Pharm (Weinheim) ; 355(5): e2100497, 2022 May.
Artigo em Inglês | MEDLINE | ID: mdl-35174898

RESUMO

The quest for isoform-selective and specific ATP-competitive protein kinase inhibitors is of great interest, as inhibitors with these qualities will come with reduced toxicity and improved efficacy. However, creating such inhibitors is very challenging due to the high molecular similarity of kinases ATP active sites. To achieve selectivity for our casein kinase (CK) 1 inhibitor series, we elected to endow our previous CK1δ-hit, 3-(4-fluorophenyl)-5-isopropyl-4-(pyridin-4-yl)isoxazole (1), with chiral iminosugar scaffolds. These scaffolds were attached to C5 of the isoxazole ring, a position deemed favorable to facilitate binding interactions with the ribose pocket/solvent-open area of the ATP binding pocket of CK1δ. Here, we describe the synthesis of analogs of 1 ((-)-/(+)-34, (-)-/(+)-48), which were prepared in 13 steps from enantiomerically pure ethyl (3R,4S)- and ethyl (3S,4R)-1-benzyl-4-[(tert-butyldimethylsilyl)oxy]-5-oxopyrrolidine-3-carboxylate ((-)-11 and (+)-11), respectively. The synthesis involved the coupling of Weinreb amide-activated chiral pyrrolidine scaffolds with 4- and 2-fluoro-4-picoline and reaction of the resulting 4-picolyl ketone intermediates ((-)-/(+)-40 and (-)-/(+)-44) with 4-fluoro-N-hydroxybenzenecarboximidoyl chloride to form the desired isoxazole ring. The activity of the compounds against human CK1δ, -ε, and -α was assessed in recently optimized in vitro assays. Compound (-)-34 was the most active compound with IC50 values (CK1δ/ε) of 1/8 µM and displayed enhanced selectivity toward CK1δ.


Assuntos
Caseína Quinase Idelta , Trifosfato de Adenosina/metabolismo , Caseína Quinase Idelta/química , Caseína Quinase Idelta/metabolismo , Humanos , Isoxazóis/química , Isoxazóis/farmacologia , Inibidores de Proteínas Quinases , Relação Estrutura-Atividade
5.
Molecules ; 27(7)2022 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-35408759

RESUMO

Bile acid receptors have been identified as important targets for the development of new therapeutics to treat various metabolic and inflammatory diseases. The synthesis of new bile acid analogues can help elucidate structure-activity relationships and define compounds that activate these receptors selectively. Towards this, access to large quantities of a chenodeoxycholic acid derivative bearing a C-12 methyl and a C-13 to C-14 double bond provided an interesting scaffold to investigate the chemical manipulation of the C/D ring junction in bile acids. The reactivity of this alkene substrate with various zinc carbenoid species showed that those generated using the Furukawa methodology achieved selective α-cyclopropanation, whereas those generated using the Shi methodology reacted in an unexpected manner giving rise to a rearranged skeleton whereby the C ring has undergone contraction to form a novel spiro-furan ring system. Further derivatization of the cyclopropanated steroid included O-7 oxidation and epimerization to afford new bile acid derivatives for biological evaluation.


Assuntos
Ácidos e Sais Biliares , Ácido Quenodesoxicólico , Ácido Quenodesoxicólico/química , Oxirredução , Esteroides , Relação Estrutura-Atividade
6.
J Am Chem Soc ; 143(42): 17666-17676, 2021 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-34664502

RESUMO

The isocitrate lyase paralogs of Mycobacterium tuberculosis (ICL1 and 2) are essential for mycobacterial persistence and constitute targets for the development of antituberculosis agents. We report that (2R,3S)-2-hydroxy-3-(nitromethyl)succinic acid (5-NIC) undergoes apparent retro-aldol cleavage as catalyzed by ICL1 to produce glyoxylate and 3-nitropropionic acid (3-NP), the latter of which is a covalent-inactivating agent of ICL1. Kinetic analysis of this reaction identified that 5-NIC serves as a robust and efficient mechanism-based inactivator of ICL1 (kinact/KI = (1.3 ± 0.1) × 103 M-1 s-1) with a partition ratio <1. Using enzyme kinetics, mass spectrometry, and X-ray crystallography, we identified that the reaction of the 5-NIC-derived 3-NP with the Cys191 thiolate of ICL1 results in formation of an ICL1-thiohydroxamate adduct as predicted. One aspect of the design of 5-NIC was to lower its overall charge compared to isocitrate to assist with cell permeability. Accordingly, the absence of the third carboxylate group will simplify the synthesis of pro-drug forms of 5-NIC for characterization in cell-infection models of M. tuberculosis.


Assuntos
Inibidores Enzimáticos/química , Isocitrato Liase/antagonistas & inibidores , Mycobacterium tuberculosis/enzimologia , Succinatos/química , Inibidores Enzimáticos/síntese química , Inibidores Enzimáticos/metabolismo , Glioxilatos/química , Glioxilatos/metabolismo , Isocitrato Liase/química , Isocitrato Liase/metabolismo , Cinética , Modelos Químicos , Nitrocompostos/química , Nitrocompostos/metabolismo , Propionatos/química , Propionatos/metabolismo , Ligação Proteica , Succinatos/síntese química , Succinatos/metabolismo
7.
Chemistry ; 27(52): 13144-13148, 2021 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-34258796

RESUMO

A dimeric ß-diketiminato ytterbium(II) hydride affects both the two-electron aromatization of 1,3,5,7-cyclooctatetraene (COT) and the more challenging two-electron reduction of polyaromatic hydrocarbons, including naphthalene (E0 =-2.60 V). Confirmed by Density Functional Theory calculations, these reactions proceed via consecutive polarized Yb-H/C=C insertion and deprotonation steps to provide the respective ytterbium (II) inverse sandwich complexes and hydrogen gas. These observations highlight the ability of a simple ytterbium(II) hydride to act as a powerful two-electron reductant at room temperature without the necessity of an external electron to initiate the reaction and avoiding radicaloid intermediates.

8.
J Org Chem ; 86(13): 8843-8850, 2021 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-34126010

RESUMO

3'-Deoxy-3',4'-didehydro-cytidine triphosphate (ddhCTP) is a novel antiviral molecule produced by the enzyme viperin as part of the innate immune response. ddhCTP has been shown to act as an obligate chain terminator of flavivirus and SARS-CoV-2 RNA-dependent RNA polymerases; however, further biophysical studies have been precluded by limited access to this promising antiviral. Herein, we report a robust and scalable synthesis of ddhCTP as well as the mono- and diphosphates ddhCMP and ddhCDP, respectively. Identification of a 2'-silyl ether protection strategy enabled selective synthesis and facile purification of the 5'-triphosphate, culminating in the preparation of ddhCTP on a gram scale.


Assuntos
Antivirais , COVID-19 , Citidina Trifosfato , Humanos , Proteínas , RNA Viral , SARS-CoV-2
9.
J Neurosci ; 39(35): 6817-6828, 2019 08 28.
Artigo em Inglês | MEDLINE | ID: mdl-31235647

RESUMO

Normal brain function requires proper targeting of synaptic-vesicle (SV) and active-zone components for presynaptic assembly and function. Whether and how synaptogenic signals (e.g., adhesion) at axo-dendritic contact sites promote axonal transport of presynaptic components for synapse formation, however, remain unclear. In this study, we show that Borderless (Bdl), a member of the conserved IgSF9-family trans-synaptic cell adhesion molecules, plays a novel and specific role in regulating axonal transport of SV components. Loss of bdl disrupts axonal transport of SV components in photoreceptor R8 axons, but does not affect the transport of mitochondria. Genetic mosaic analysis, transgene rescue and cell-type-specific knockdown indicate that Bdl is required both presynaptically and postsynaptically for delivering SV components in R8 axons. Consistent with a role for Bdl in R8 axons, loss of bdl causes a failure of R8-dependent phototaxis response to green light. bdl interacts genetically with imac encoding for a member of the UNC-104/Imac/KIF1A-family motor proteins, and is required for proper localization of Imac in R8 presynaptic terminals. Our results support a model in which Bdl mediates specific axo-dendritic interactions in a homophilic manner, which upregulates the Imac motor in promoting axonal transport of SV components for R8 presynaptic assembly and function.SIGNIFICANCE STATEMENT Whether and how synaptogenic adhesion at axo-dendritic contact sites regulates axonal transport of presynaptic components remain unknown. Here we show for the first time that a trans-synaptic adhesion molecule mediates specific interactions at axo-dendritic contact sites, which is required for upregulating the UNC-104/Imac/KIF1A motor in promoting axonal transport of synaptic-vesicle components for presynaptic assembly and function.


Assuntos
Transporte Axonal/fisiologia , Visão de Cores/fisiologia , Proteínas de Drosophila/metabolismo , Proteínas de Membrana/metabolismo , Terminações Pré-Sinápticas/metabolismo , Vesículas Sinápticas/metabolismo , Animais , Animais Geneticamente Modificados , Axônios/metabolismo , Dendritos/metabolismo , Drosophila , Proteínas de Drosophila/genética , Proteínas de Membrana/genética , Mitocôndrias/metabolismo , Sinapses/metabolismo
10.
Org Biomol Chem ; 18(25): 4728-4733, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32531013

RESUMO

Late oxidation of hexose based building blocks or the use of uronic acid containing building blocks are two complementary strategies in the synthesis of glycosaminoglycans, the latter simplifiying the later stages of the process. Here we report the synthesis and evaluation of various disaccharide donors-uronic acids and their pyranose equivalents-for the synthesis of heparan sulfate, using an established protective group strategy. Hexose based "imidate" type donors perform well in the studied glycosylations, while their corresponding uronate esters fall short; a uronate ester thioglycoside performs equal to, if not better than, a hexose thioglycoside equivalent.

11.
J Labelled Comp Radiopharm ; 62(2): 67-76, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30548247

RESUMO

Morquio A syndrome is an autosomal mucopolysaccharide storage disorder that leads to accumulation of keratan sulfate. Diagnosis of this disease can be aided by measuring the levels of keratan sulfate in the urine. This requires the liquid chromatography tandem mass spectrometry (LCMS/MS) measurement of sulfated N-acetyl-d-lactosamines in the urine after cleavage of the keratan sulfate with keratanase II. Quantification requires isotopically-labelled internal standards. The synthesis of these 13 C6 -labelled standards from 13 C6 -galactose and N-acetylglucosamine is described. The required protected disaccharide is prepared utilising a regioselective, high yielding ß-galactosylation of a partially protected glucosamine acceptor and an inverse addition protocol. Subsequent synthesis of the 13 C6 -labelled mono and disulfated N-acetyllactosamines was achieved in five and eight steps, respectively, from this intermediate to provide internal standards for the LCMS/MS quantification of keratan sulfate in urine.


Assuntos
Acetilgalactosamina/análogos & derivados , Espectrometria de Massas/métodos , Técnicas de Diagnóstico Molecular/métodos , Acetilgalactosamina/síntese química , Isótopos de Carbono/química , Sulfato de Queratano/análise , Sulfato de Queratano/urina , Mucopolissacaridose IV/urina
12.
J Biol Chem ; 292(38): 15907-15915, 2017 09 22.
Artigo em Inglês | MEDLINE | ID: mdl-28794158

RESUMO

Purine nucleoside phosphorylase (PNP) is part of the human purine salvage pathway. Its deficiency triggers apoptosis of activated T-cells, making it a target for T-cell proliferative disorders. Transition-state analogues of PNP bind with picomolar (pm) dissociation constants. Tight-binding PNP inhibitors show exceptionally long lifetimes on the target enzyme. We solve the mechanism of the target residence time by comparing functional off-rates in vitro and in vivo We report in vitro PNP-inhibitor dissociation rates (t½) from 3 to 31 min for seven Immucillins with dissociation constants of 115 to 6 pm Treatment of human erythrocytes with DADMe-Immucillin-H (DADMe-ImmH, 22 pm) causes complete inhibition of PNP. Loss of [14C]DADMe-ImmH from erythrocytes during multiple washes is slow and biphasic, resulting from inhibitor release and rebinding to PNP catalytic sites. The slow phase gave a t½ of 84 h. Loss of [14C]DADMe-ImmH from erythrocytes in the presence of excess unlabeled DADMe-ImmH increased to a t½ of 1.6 h by preventing rebinding. Thus, in human erythrocytes, rebinding of DADMe-ImmH is 50-fold more likely than diffusional loss of the inhibitor from the erythrocyte. Humans treated with a single oral dose of DADMe-ImmH in phase 1 clinical trials exhibit regain of PNP activity with a t½ of 59 days, corresponding to the erythropoiesis rate in humans. Thus, the PNP catalytic site recapture of DADMe-ImmH is highly favored in vivo We conclude that transition-state analogues with picomolar dissociation constants exhibit long lifetimes on their targets in vivo because the probability of the target enzyme recapturing inhibitor molecules is greater than diffusional loss to the extracellular space.


Assuntos
Inibidores Enzimáticos/metabolismo , Inibidores Enzimáticos/farmacologia , Espaço Intracelular/metabolismo , Purina-Núcleosídeo Fosforilase/antagonistas & inibidores , Transporte Biológico , Ensaios Clínicos Fase I como Assunto , Enzimas , Eritrócitos/efeitos dos fármacos , Eritrócitos/enzimologia , Humanos , Espaço Intracelular/efeitos dos fármacos , Ligação Proteica , Purina-Núcleosídeo Fosforilase/metabolismo , Pirrolidinas/metabolismo , Pirrolidinas/farmacologia
13.
Inorg Chem ; 57(5): 2480-2488, 2018 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-29442503

RESUMO

Development of a new and high yielding synthetic route to 1,8-diformyl-carbazoles 3 (3a 3,6-di- tert-butyl substituted; 3b 3,6-unsubstituted) is reported. Use of a Heck coupling reaction, followed by ozonolysis, has greatly facilitated the preparation of these interesting head units in useful quantities. An initial foray into the new generations of Schiff base macrocycles that ready access to these head units (3) opens up, has led to the direct (i.e., metal-free) synthesis of two [2 + 2] macrocycles from 3a or 3b with 1,2-diaminoethane, H2LtBu (4a) and H2LH (4b), respectively, obtained as yellow powders in high yields (87-88%). The dizinc complex [Zn2LH(OAc)2] (5b) was isolated as a bright yellow solid in 83% yield, by 1:2:2 reaction of H2LH with zinc(II) acetate and triethylamine. Aldehydes 3a and 3b, macrocycle H2LH, and complex [Zn2LH(OAc)2] (5b) have been structurally characterized. The carbazole NH makes bifurcated hydrogen bonds with the pair of flanking 1,8-diformyl-moieties in 3, or 1,8-diimine-moieties in H2LH, leading to a flat, all- cis conformation. The stepped conformation of the metal-free macrocycle H2LH is retained in [Zn2LH(OAc)2], despite deprotonation and binding of two zinc(II) centers within the two tridentate pockets. The N3O2 coordination of the zinc ions is completed by one µ1,1- and one µ1,3- bridging acetate anion. Excitation of nanomolar [Zn2LH(OAc)2] in DMF at 335 nm results in clearly visible blue fluorescence (λmax = 460 nm). Further studies on the H2LH macrocycle revealed turn-on fluorescence, with selectivity (over Ca2+, Mg2+ and a range of 3d dications) and nanomolar sensitivity for zinc(II) ions, highlighting one of the many potential applications for these new carbazole-based Schiff base macrocycles.

14.
Echocardiography ; 35(10): 1692-1694, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30099768

RESUMO

Kawasaki disease (KD) is a vasculitis that affects medium-sized arteries and can lead to coronary artery aneurysms. KD should be considered in any infant presenting with prolonged fever. Delaying treatment beyond Day 10 of fever portends a high risk of coronary artery aneurysms. Echocardiography is often necessary to diagnose KD in young infants who frequently present without classic physical examination findings. We report on a case of KD with giant aneurysms in a 2-month-old infant. A combination of transthoracic echocardiography and CT angiography was utilized in the diagnosis as well as in the management of this infant.


Assuntos
Angiografia por Tomografia Computadorizada/métodos , Aneurisma Coronário/diagnóstico por imagem , Angiografia Coronária/métodos , Ecocardiografia/métodos , Síndrome de Linfonodos Mucocutâneos/diagnóstico por imagem , Vasos Coronários/diagnóstico por imagem , Diagnóstico Diferencial , Feminino , Humanos , Lactente
15.
J Am Chem Soc ; 138(10): 3403-9, 2016 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-26927977

RESUMO

The relevance of sub-picosecond protein motions to the catalytic event remains a topic of debate. Heavy enzymes (isotopically substituted) provide an experimental tool for bond-vibrational links to enzyme catalysis. A recent transition path sampling study with heavy purine nucleoside phosphorylase (PNP) characterized the experimentally observed mass-dependent slowing of barrier crossing (Antoniou, D.; Ge, X.; Schramm, V. L.; Schwartz, S. D. J. Phys. Chem. Lett. 2012, 3, 3538). Here we computationally identify second-sphere amino acid residues predicted to influence the freedom of the catalytic site vibrational modes linked to heavy enzyme effects in PNP. We mutated heavy and light PNPs to increase the catalytic site vibrational freedom. Enzymatic barrier-crossing rates were converted from mass-dependent to mass-independent as a result of the mutations. The mutagenic uncoupling of femtosecond motions between catalytic site groups and reactants decreased transition state barrier crossing by 2 orders of magnitude, an indication of the femtosecond dynamic contributions to catalysis.


Assuntos
Purina-Núcleosídeo Fosforilase/química , Purina-Núcleosídeo Fosforilase/genética , Biocatálise , Domínio Catalítico , Cristalografia por Raios X , Humanos , Modelos Moleculares , Mutagênese Sítio-Dirigida , Purina-Núcleosídeo Fosforilase/antagonistas & inibidores , Purina-Núcleosídeo Fosforilase/metabolismo , Relação Estrutura-Atividade
16.
Anal Chem ; 88(23): 11860-11867, 2016 12 06.
Artigo em Inglês | MEDLINE | ID: mdl-27779859

RESUMO

5'-Methylthioadenosine phosphorylase (MTAP) and 5'-methylthioadenosine nucleosidase (MTAN) catalyze the phosphorolysis and hydrolysis of 5'-methylthioadenosine (MTA), respectively. Both enzymes have low KM values for their substrates. Kinetic assays for these enzymes are challenging, as the ultraviolet absorbance spectra for reactant MTA and product adenine are similar. We report a new assay using 2-amino-5'-methylthioadenosine (2AMTA) as an alternative substrate for MTAP and MTAN enzymes. Hydrolysis or phosphorolysis of 2AMTA forms 2,6-diaminopurine, a fluorescent and easily quantitated product. We kinetically characterize 2AMTA with human MTAP, bacterial MTANs and use 2,6-diaminopurine as a fluorescent substrate for yeast adenine phosphoribosyltransferase. 2AMTA was used as the substrate to kinetically characterize the dissociation constants for three-transition-state analogue inhibitors of MTAP and MTAN. Kinetic values obtained from continuous fluorescent assays with MTA were in good agreement with previously measured literature values, but gave smaller experimental errors. Chemical synthesis from ribose and 2,6-dichloropurine provided crystalline 2AMTA as the oxalate salt. Chemo-enzymatic synthesis from ribose and 2,6-diaminopurine produced 2-amino-S-adenosylmethionine for hydrolytic conversion to 2AMTA. Interaction of 2AMTA with human MTAP was also characterized by pre-steady-state kinetics and by analysis of the crystal structure in a complex with sulfate as a catalytically inert analogue of phosphate. This assay is suitable for inhibitor screening by detection of fluorescent product, for quantitative analysis of hits by rapid and accurate measurement of inhibition constants in continuous assays, and pre-steady-state kinetic analysis of the target enzymes.


Assuntos
Adenina/metabolismo , Ensaios Enzimáticos/métodos , Fluorescência , 2-Aminopurina/análogos & derivados , 2-Aminopurina/química , 2-Aminopurina/metabolismo , Adenina/análogos & derivados , Adenina/análise , Adenina Fosforribosiltransferase/metabolismo , Humanos , Cinética , Saccharomyces cerevisiae/enzimologia , Especificidade por Substrato
17.
Biochemistry ; 54(15): 2520-9, 2015 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-25806409

RESUMO

5'-Methylthioadenosine/S-adenosyl-l-homocysteine nucleosidases (MTANs) catalyze the hydrolysis of 5'-methylthioadenosine to adenine and 5-methylthioribose. The amino acid sequences of the MTANs from Vibrio cholerae (VcMTAN) and Escherichia coli (EcMTAN) are 60% identical and 75% similar. Protein structure folds and kinetic properties are similar. However, binding of transition-state analogues is dominated by favorable entropy in VcMTAN and by enthalpy in EcMTAN. Catalytic sites of VcMTAN and EcMTAN in contact with reactants differ by two residues; Ala113 and Val153 in VcMTAN are Pro113 and Ile152, respectively, in EcMTAN. We mutated the VcMTAN catalytic site residues to match those of EcMTAN in anticipation of altering its properties toward EcMTAN. Inhibition of VcMTAN by transition-state analogues required filling both active sites of the homodimer. However, in the Val153Ile mutant or double mutants, transition-state analogue binding at one site caused complete inhibition. Therefore, a single amino acid, Val153, alters the catalytic site cooperativity in VcMTAN. The transition-state analogue affinity and thermodynamics in mutant VcMTAN became even more unlike those of EcMTAN, the opposite of expectations from catalytic site similarity; thus, catalytic site contacts in VcMTAN are unable to recapitulate the properties of EcMTAN. X-ray crystal structures of EcMTAN, VcMTAN, and a multiple-site mutant of VcMTAN most closely resembling EcMTAN in catalytic site contacts show no major protein conformational differences. The overall protein architectures of these closely related proteins are implicated in contributing to the catalytic site differences.


Assuntos
Proteínas de Escherichia coli/química , Escherichia coli/enzimologia , N-Glicosil Hidrolases/química , Vibrio cholerae/enzimologia , Difosfato de Adenosina/análogos & derivados , Difosfato de Adenosina/química , Difosfato de Adenosina/genética , Difosfato de Adenosina/metabolismo , Alanina/química , Alanina/genética , Alanina/metabolismo , Substituição de Aminoácidos , Catálise , Domínio Catalítico , Cristalografia por Raios X , Escherichia coli/genética , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Mutação de Sentido Incorreto , N-Glicosil Hidrolases/genética , N-Glicosil Hidrolases/metabolismo , Tionucleotídeos/química , Tionucleotídeos/genética , Tionucleotídeos/metabolismo , Valina/química , Valina/genética , Valina/metabolismo , Vibrio cholerae/genética
18.
J Am Chem Soc ; 137(45): 14275-80, 2015 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-26494017

RESUMO

Helicobacter pylori is a Gram-negative bacterium that colonizes the gut of over 50% of the world's population. It is responsible for most peptic ulcers and is an important risk factor for gastric cancer. Antibiotic treatment for H. pylori infections is challenging as drug resistance has developed to antibiotics with traditional mechanisms of action. H. pylori uses an unusual pathway for menaquinone biosynthesis with 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) catalyzing an essential step. We validated MTAN as a target with a transition-state analogue of the enzyme [Wang, S.; Haapalainen, A. M.; Yan, F.; et al. Biochemistry 2012, 51, 6892-6894]. MTAN inhibitors will only be useful drug candidates if they can both include tight binding to the MTAN target and have the ability to penetrate the complex cell membrane found in Gram-negative H. pylori. Here we explore structural scaffolds for MTAN inhibition and for growth inhibition of cultured H. pylori. Sixteen analogues reported here are transition-state analogues of H. pylori MTAN with dissociation constants of 50 pM or below. Ten of these prevent growth of the H. pylori with IC90 values below 0.01 µg/mL. These remarkable compounds meet the criteria for potent inhibition and cell penetration. As a consequence, 10 new H. pylori antibiotic candidates are identified, all of which prevent H. pylori growth at concentrations 16-2000-fold lower than the five antibiotics, amoxicillin, metronidazole, levofloxacin, tetracyclin, and clarithromycin, commonly used to treat H. pylori infections. X-ray crystal structures of MTAN cocrystallized with several inhibitors show them to bind in the active site making interactions consistent with transition-state analogues.


Assuntos
Antibacterianos/farmacologia , Helicobacter pylori/efeitos dos fármacos , Antibacterianos/síntese química , Antibacterianos/química , Relação Dose-Resposta a Droga , Testes de Sensibilidade Microbiana , Modelos Moleculares , Relação Estrutura-Atividade
19.
Bioorg Med Chem ; 23(17): 5326-33, 2015 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-26260335

RESUMO

MTDIA is a picomolar transition state analogue inhibitor of human methylthioadenosine phosphorylase and a femtomolar inhibitor of Escherichia coli methylthioadenosine nucleosidase. MTDIA has proven to be a non-toxic, orally available pre-clinical drug candidate with remarkable anti-tumour activity against a variety of human cancers in mouse xenografts. The structurally similar compound MTDIH is a potent inhibitor of human and malarial purine nucleoside phosphorylase (PNP) as well as the newly discovered enzyme, methylthioinosine phosphorylase, isolated from Pseudomonas aeruginosa. Since the enantiomers of some pharmaceuticals have revealed surprising biological activities, the enantiomers of MTDIH and MTDIA, compounds 1 and 2, respectively, were prepared and their enzyme binding properties studied. Despite binding less tightly to their target enzymes than their enantiomers compounds 1 and 2 are nanomolar inhibitors.


Assuntos
Adenina/análogos & derivados , Escherichia coli/enzimologia , Plasmodium falciparum/enzimologia , Pseudomonas aeruginosa/enzimologia , Purina-Núcleosídeo Fosforilase/antagonistas & inibidores , Pirrolidinas/química , Pirrolidinas/farmacologia , Adenina/química , Adenina/farmacologia , Descoberta de Drogas , Escherichia coli/efeitos dos fármacos , Humanos , Modelos Moleculares , Neoplasias/tratamento farmacológico , Neoplasias/enzimologia , Plasmodium falciparum/efeitos dos fármacos , Ligação Proteica , Pseudomonas aeruginosa/efeitos dos fármacos , Purina-Núcleosídeo Fosforilase/metabolismo , Estereoisomerismo
20.
Inorg Chem ; 53(6): 3126-40, 2014 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-24559053

RESUMO

A series of dipyrido[3,2-a:2',3'-c]phenazine (dppz)-based ligands with electron-withdrawing substituents and their [Re(CO)3(L)Cl] and [Re(CO)3(L)(py)]PF6 complexes have been studied using Raman, resonance Raman, and transient resonance Raman (TR(2)) and time-resolved infrared (TRIR) spectroscopic techinques in conjunction with computational chemistry as well as electrochemical studies, emission, and absorption of ground and excited states. DFT (B3LYP) frequency calculations show good agreement with nonresonant Raman spectra, which allowed these to be used to identify phenanthroline, phenazine, and delocalized modes. These band assignments were used to establish the nature of chromophores active in resonance Raman spectra, probed with wavelengths between 350.7 and 457.9 nm. X-ray crystallography of [Re(CO)3(dppzBr2)Cl] and [Re(CO)3(dppzBr)(py)]PF6 showed these crystallize in space groups triclinic P1 and monoclinic P2(1/n), respectively. Electrochemical studies showed that substituents have a strong effect on the phenazine MO, changing the reduction potential by 200 mV. Transient absorption studies showed that generally the [Re(CO)3(L)(py)]PF6 complexes had longer lifetimes than the corresponding [Re(CO)3(L)Cl] complexes; the probed state is likely to be (3)π → π* (phz) in nature. TR(2) spectra of the ligands provided a marker for the triplet π → π* state, and the TR(2) spectra of the complexes suggest an intraligand (IL) π,π* state for [Re(CO)3(L)(py)](+) complexes, and a potentially mixed IL/MLCT state for [Re(CO)3(L)Cl] complexes. TRIR spectroscopy is more definitive with THEXI state assignments, and analysis of the metal-carbonyl region (1800-2100 cm(-1)) on the picosecond and nanosecond time scales indicates the formation of MLCT(phen/phz) states for all [Re(CO)3(L)Cl] complexes, and IL π → π* (phen) states for all [Re(CO)3(L)(py)](+) complexes, with all but [Re(CO)3(dppzBr(CF3))(py)](+) showing some contribution from an MLCT(phen) state also.

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