Inhibition of bacterial growth and galactosyltransferase activity of WbwC by α, ω-bis(3-alkyl-1H-imidazolium)alkane salts: Effect of varying carbon content.

A series of compounds was designed and synthesized having two imidazolium rings separated by a polymethylene spacer and having alkyl substituents on each of the imidazolium rings. The compounds were assayed for their effects on the activity of galactosyltransferase WbwC, and also on the growth of Gram-negative and Gram-positive bacteria, as well as human cells. The inhibition observed on enzyme activities and cell growth was dependent on the total number of carbons in the spacer and the alkyl substituents on the imidazolium rings.

Structural Insights into Azole-based Inhibitors of Heme Oxygenase-1: Development of Selective Compounds for Therapeutic Applications.

The development of isozyme-selective heme oxygenase (HO) inhibitors promises powerful pharmacological tools to elucidate the regulatory characteristics of the HO system. It is already known that HO has cytoprotective properties with a role in several disease states; thus, it is an enticing therapeutic target. Historically, the metalloporphyrins have been used as competitive HO inhibitors based on their structural similarity to the substrate, heme.

Antitumor effect of a liposome-encapsulated β1,4-galactosyltransferase inhibitor.

Galactosyltransferases are a family of enzymes responsible for the synthesis of glycan chains which are involved in cell proliferation, adhesion and apoptosis. A recently synthesized galactosyltransferase inhibitor, 2-naphthyl 2-butanamido-2-deoxy-1-thio-β-D-glucopyranoside (612), has been found to selectively inhibit β1,4-galactosyltransferase over β1,3-galactosyltransferase and, therefore, has potential to suppress the synthesis of cancer associated epitopes. However, the application of this inhibitory activity in biological systems remains unknown.

Identification and biochemical characterization of WbwB, a novel UDP-Gal: Neu5Ac-R α1,4-galactosyltransferase from the intestinal pathogen Escherichia coli serotype O104.

The intestinal pathogen Escherichia coli serotype O104:H4 (ECO104) can cause bloody diarrhea and haemolytic uremic syndrome. The ECO104 O antigen has the unique repeating unit structure [4Galα1-4Neu5,7,9Acα2-3Galβ1-3GalNAcβ1-], which includes the mammalian sialyl-T antigen as an internal structure. Previously, we identified WbwC from ECO104 as the β3Gal-transferase that synthesizes the T antigen, and showed that α3-sialyl-transferase WbwA transfers sialic acid to the T antigen.

Differential inhibition of rat and mouse microsome heme oxygenase by derivatives of imidazole and benzimidazole.

Metalloporphyrin heme oxygenase (HO) inhibitors have made an important contribution to elucidating the role of HO in physiological processes. Nevertheless, their off-target effects have drawn substantial criticism, which prompted us to develop non-porphyrin, azole-based inhibitors of HO. These second-generation HO inhibitors were evaluated using spleen and brain microsomes from rats as native sources of HO-1 and HO-2, respectively.

Cysteine-independent activation/inhibition of heme oxygenase-2.

Reactive thiols of cysteine (cys) residues in proteins play a key role in transforming chemical reactivity into a biological response. The heme oxygenase-2 (HO-2) isozyme contains two cys residues that have been implicated in binding of heme and also the regulation of its activity. In this paper, we address the question of a role for cys residues for the HO-2 inhibitors or activators designed in our laboratory.

Human acetyl-CoA:glucosamine-6-phosphate N-acetyltransferase 1 has a relaxed donor specificity and transfers acyl groups up to four carbons in length.

Glucosamine-6-phosphate N-acetyltransferase1 (GNA1) catalyses the transfer of an acetyl group from acetyl coenzyme A (AcCoA) to glucosamine-6-phosphate (GlcN6P) to form N-acetylglucosamine-6-phosphate (GlcNAc6P), which is an essential intermediate in UDP-GlcNAc biosynthesis. An analog of GlcNAc, N-butyrylglucosamine (GlcNBu) has shown healing properties for bone and articular cartilage in animal models of arthritis. The goal of this work was to examine whether GNA1 has the ability to transfer a butyryl group from butyryl-CoA to GlcN6P to form GlcNBu6P, which can then be converted to GlcNBu.

Identification and Biochemical Characterization of the Novel α2,3-Sialyltransferase WbwA from Pathogenic Escherichia coli Serotype O104.

Unlabelled: The sialyl-T antigen sialylα2-3Galβ1-3GalNAc is a common O-glycan structure in human glycoproteins and is synthesized by sialyltransferase ST3Gal1. The enterohemorrhagic Escherichia coli serotype O104 has the rare ability to synthesize a sialyl-T antigen mimic. We showed here that the wbwA gene of the E.

Structure-Activity Relationships of 1,2-Disubstituted Benzimidazoles: Selective Inhibition of Heme Oxygenase-2 Activity.

Devising ways to up- or down-regulate heme oxygenase activity is attracting much interest as a strategy for the treatment of a variety of disorders. With a view of obtaining compounds that exhibit high potency and selectivity as inhibitors of the heme oxygenase-2 (HO-2) isozyme (constitutive) relative to the heme oxygenase-1 (HO-1) isozyme (inducible), several 1,2-disubstituted 1H-benzimidazoles were designed and synthesized. Specifically, analogues were synthesized in which the C2 substituent was the following: (1H-imidazol-1-yl)methyl, (N-morpholinyl)methyl, cyclopentylmethyl, cyclohexylmethyl, or (norborn-2-yl)methyl.

Biosynthesis of the Common Polysaccharide Antigen of Pseudomonas aeruginosa PAO1: Characterization and Role of GDP-D-Rhamnose:GlcNAc/GalNAc-Diphosphate-Lipid α1,3-D-Rhamnosyltransferase WbpZ.

Unlabelled: The opportunistic pathogen Pseudomonas aeruginosa produces two major cell surface lipopolysaccharides, characterized by distinct O antigens, called common polysaccharide antigen (CPA) and O-specific antigen (OSA). CPA contains a polymer of D-rhamnose (D-Rha) in α1-2 and α1-3 linkages. Three putative glycosyltransferase genes, wbpX, wbpY, and wbpZ, are part of the CPA biosynthesis cluster.

Curcumin-induced heme oxygenase-1 expression prevents H2O2-induced cell death in wild type and heme oxygenase-2 knockout adipose-derived mesenchymal stem cells.

Mesenchymal stem cell (MSC) administration is a promising adjuvant therapy to treat tissue injury. However, MSC survival after administration is often hampered by oxidative stress at the site of injury. Heme oxygenase (HO) generates the cytoprotective effector molecules biliverdin/bilirubin, carbon monoxide (CO) and iron/ferritin by breaking down heme.

Neurotherapeutic effects of novel HO-1 inhibitors in vitro and in a transgenic mouse model of Alzheimer's disease.

Heme oxygenase-1 (HO-1) encoded by the HMOX1 gene is a 32-kDa stress protein that catabolizes heme to biliverdin, free iron, and carbon monoxide (CO). Glial HO-1 is over-expressed in the CNS of subjects with Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). The HMOX1 gene is exquisitely sensitive to oxidative stress and is induced in brain and other tissues in various models of disease and trauma.

Characterization of two UDP-Gal:GalNAc-diphosphate-lipid β1,3-galactosyltransferases WbwC from Escherichia coli serotypes O104 and O5.

Escherichia coli displays O antigens on the outer membrane that play an important role in bacterial interactions with the environment. The O antigens of enterohemorrhagic E. coli O104 and O5 contain a Galβ1-3GalNAc disaccharide at the reducing end of the repeating unit.

Synthesis and anti-Plasmodium activity of benzimidazole analogues structurally related to astemizole.

A series of compounds structurally related to astemizole were designed and synthesized with the goal of determining their anti-Plasmodium activity. Several modifications of the astemizole structure, namely the removal of the 4-fluorobenzyl and/or 4-methoxyphenethyl moieties, substitution of the benzene ring of the benzimidazole scaffold, replacement of the fluorine atom in the 4-fluorobenzyl group, and variation of the 4-aminopiperidine moiety, were explored. In vitro evaluation of the anti-Plasmodium activity of these compounds using the ItG strain showed that astemizole and some of its structurally similar derivatives have IC50 values in the nanomolar range and exhibit toxicity towards the parasite over Chinese ovarian hamster (CHO) cells with a selectivity as high as 200.

Selective inhibition of heme oxygenase-2 activity by analogs of 1-(4-chlorobenzyl)-2-(pyrrolidin-1-ylmethyl)-1H-benzimidazole (clemizole): Exploration of the effects of substituents at the N-1 position.

Several analogs based on the lead structure of 1-(4-chlorobenzyl)-2-(pyrrolidin-1-ylmethyl)-1H-benzimidazole (clemizole) were synthesized and evaluated as novel inhibitors of heme oxygenase (HO). Many of the compounds were found to be potent and highly selective for the HO-2 isozyme (constitutive), and had substantially less inhibitory activity on the HO-1 isozyme (inducible). The compounds represent the first report of highly potent and selective inhibitors of HO-2 activity, and complement our suite of selective HO-1 inhibitors.

Acceptor specificities and selective inhibition of recombinant human Gal- and GlcNAc-transferases that synthesize core structures 1, 2, 3 and 4 of O-glycans.

Background: Modifications of proteins by O-glycosylation determine many of the properties and functions of proteins. We wish to understand the mechanisms of O-glycosylation and develop inhibitors that could affect glycoprotein functions and alter cellular behavior.

Methods: We expressed recombinant soluble human Gal- and GlcNAc-transferases that synthesize the O-glycan cores 1 to 4 and are critical for the overall structures of O-glycans.

The interaction of imidazole-, imidazolium-, and tetrazolium-containing compounds with DNA.

The interaction between DNA and members of series of bivalent imidazole compounds, monovalent and bivalent imidazolium compounds, and monovalent and bivalent tetrazolium compounds, which had been synthesized and evaluated for their anti-Plasmodium activity, has been examined using the displacement of SYBR Green I as a measure of competitive binding. The degree of interaction with DNA appears to be dependent on both hydrophobic and charge-pairing interactions.

Selective inhibition of glycosyltransferases by bivalent imidazolium salts.

Galactosyltransferases (GalTs) extend the glycan chains of mammalian glycoproteins by adding Gal to terminal GlcNAc residues, and thus build the scaffolds for biologically important glycan structures. We have shown that positively charged bivalent imidazolium salts in which the two imidazolium groups are linked by an aliphatic chain of 20 or 22 carbons form potent inhibitors of purified human β3-GalT5, using GlcNAcβ-benzyl as acceptor substrate. The inhibitors are not substrate analogs and also inhibited a selected number of other glycosyltransferases.

Structural insights into human heme oxygenase-1 inhibition by potent and selective azole-based compounds.

The development of heme oxygenase (HO) inhibitors, especially those that are isozyme-selective, promises powerful pharmacological tools to elucidate the regulatory characteristics of the HO system. It is already known that HO has cytoprotective properties and may play a role in several disease states, making it an enticing therapeutic target. Traditionally, the metalloporphyrins have been used as competitive HO inhibitors owing to their structural similarity with the substrate, heme.

Biochemical characterization of WbdN, a β1,3-glucosyltransferase involved in O-antigen synthesis in enterohemorrhagic Escherichia coli O157.

The enterohemorrhagic O157 strain of Escherichia coli, which is one of the most well-known bacterial pathogens, has an O-antigen repeating unit structure with the sequence [-2-d-Rha4NAcα1-3-l-Fucα1-4-d-Glcβ1-3-d-GalNAcα1-]. The O-antigen gene cluster of E. coli O157 contains the genes responsible for the assembly of this repeating unit and includes wbdN.

Heme oxygenase inhibition by α-(1H-imidazol-1-yl)-ω-phenylalkanes: effect of introduction of heteroatoms in the alkyl linker.

Several α-(1H-imidazol-1-yl)-ω-phenylalkanes were synthesized and evaluated as novel inhibitors of heme oxygenase (HO). These compounds were found to be potent and selective for the stress-induced isozyme HO-1, showing mostly weak activity toward the constitutive isozyme HO-2. The introduction of an oxygen atom in the alkyl linker produced analogues with decreased potency toward HO-1, whereas the presence of a sulfur atom in the linker gave rise to analogues with greater potency toward HO-1 than the carbon-containing analogues.

A novel, "double-clamp" binding mode for human heme oxygenase-1 inhibition.

The development of heme oxygenase (HO) inhibitors is critical in dissecting and understanding the HO system and for potential therapeutic applications. We have established a program to design and optimize HO inhibitors using structure-activity relationships in conjunction with X-ray crystallographic analyses. One of our previous complex crystal structures revealed a putative secondary hydrophobic binding pocket which could be exploited for a new design strategy by introducing a functional group that would fit into this potential site.

Selective activation of heme oxygenase-2 by menadione.

While substantial progress has been made in elucidating the roles of heme oxygenases-1 (HO-1) and -2 (HO-2) in mammals, our understanding of the functions of these enzymes in health and disease is still incomplete. A significant amount of our knowledge has been garnered through the use of nonselective inhibitors of HOs, and our laboratory has recently described more selective inhibitors for HO-1. In addition, our appreciation of HO-1 has benefitted from the availability of tools for increasing its activity through enzyme induction.

The anti-malarial activity of bivalent imidazolium salts.

A series of compounds containing bivalent imidazolium rings and one triazolium analog were synthesized and evaluated for their ability to inhibit the replication of Plasmodium falciparum cultures. The activity and selectivity of the compounds for P. falciparum cultures were found to depend on the presence of electron-deficient rings that were spaced an appropriate distance apart.