Auxin-like activity of 1,2-benzisothiazole derivatives

The 1,2-benzisothiazol-3-yl-acetic and -3-yl-butyric acids and their ethyl esters, amides and nitriles are generally active in the split pea stem test, induce an increase in both length and fresh weight of pea internodes, inhibit the development of pea roots, and, with some exceptions (1,2-benzisothiazol-3-yl-butyric amide and nitrile), induce the production of ethylene by pea segments. Moreover they stimulate cell multiplication and raise the degree of hydration of Helianthus tuberosus explants grown in vitro. These activities are often similar or sometimes higher than those of IAA. By contrast, the 1,2-benzisothiazole derivatives having a side chain with an odd number of carbon atoms (-3-yl-carboxylic and propionic acids, amides, ethyl esters and nitriles) are inactive or show a far lower activity.     

Characterization of 1,2-dibromoethane-degrading haloalkane dehalogenase from Bradyrhizobium japonicum USDA110

Haloalkane dehalogenases (DHAs, E.C. 3.8.1.5) are very promising biocatalytic tools for the bioremediation of environmental pollutants which consists of haloalkanes. In the present work, we investigated the DHA from Bradyrhizobium japonicum USDA110 (BjDHA). The dehalogenase activity of B. japonicum USDA110 and RT-PCR analysis revealed that the BjDHA gene expression is induced by 1,2-dibromoethane (1,2-DBE) during the early exponential phase. The BjDHA gene was cloned, expressed in Escherichia coli BL21 (DE3) and characterized. The enzyme catalyzes the irreversible hydrolysis of a variety of haloalkanes to the corresponding alcohol, halide, and a hydrogen ion. The catalytic properties of the recombinant enzyme were investigated and the kinetic parameters (K_m, k_cat) for a number of substrates were determined. The results showed that the BjDHA displays wide substrate specificity towards haloalkanes and particular high activity towards 1,2-DBE. The enzyme has a different catalytic triad topology compared to the Xanthobacter haloalkane dehalogenase and is more similar to the Rhodococcus enzyme. In addition, consistent with its broad specificity, the BjDHA has a substantially larger and more polar active site cavity compared to the Xanthobacter and Rhodococcus enzymes and as a consequence, BjDHA is able to dehalogenate longer and polar compounds. These properties make this enzyme very promising bioremediation tool for environmental applications.     

Identification of Chloroacetaldehyde Dehydrogenase Involved in 1,2-Dichloroethane Degradation

The degradation of 1,2-dichloroethane and 2-chloroethanol by Xanthobacter autotrophicus GJ10 proceeds via chloroacetaldehyde, a reactive and potentially toxic intermediate. The organism produced at least three different aldehyde dehydrogenases, of which one is plasmid encoded. Two mutants of strain GJ10, designated GJ10M30 and GJ10M41, could no longer grow on 2-chloroethanol and were found to lack the NAD-dependent aldehyde dehydrogenase that is the predominant protein in wild-type cells growing on 2-chloroethanol. Mutant GJ10M30, selected on the basis of its resistance to 1,2-dibromoethane, also had lost haloalkane dehalogenase activity and Hg²⁺ resistance, indicating plasmid loss. From a gene bank of strain GJ10, different clones that complemented one of these mutants were isolated. In both transconjugants, the aldehyde dehydrogenase that was absent in the mutants was overexpressed. The enzyme was purified and was a tetrameric protein of 55-kDa subunits. The substrate range was rather broad, with the highest activity measured for acetaldehyde. The K_m value for chloroacetaldehyde was 160 μM, higher than those for other aldehydes tested. It is concluded that the ability of GJ10 to grow with 2-chloroethanol is due to the high expression level of an aldehyde dehydrogenase with a rather low activity for chloroacetaldehyde.     

Discovery of an Escherichia coli Esterase with High Activity and Enantioselectivity toward 1,2-O-Isopropylideneglycerol Esters

Escherichia coli has been widely used as an expression host for the identification of desired biocatalysts through screening or selection assays. We have previously used E. coli in growth selection and screening assays for identification of Bacillus subtilis lipase variants (located in the periplasm) with improved activity and enantioselectivity toward 1,2-O-isopropylideneglycerol (IPG) esters. In the course of these studies, we discovered that E. coli itself exhibits significant cytoplasmic esterase activity toward IPG esters. In order to identify the enzyme (or enzymes) responsible for this esterase activity, we analyzed eight E. coli knockout strains, in which single esterase genes were deleted, for their ability to hydrolyze IPG butyrate. This approach led to the identification of esterase YbfF as the major E. coli enzyme responsible for the hydrolytic activity toward IPG esters. The gene coding for YbfF was cloned and overexpressed in E. coli, and the corresponding protein was purified and characterized for its biocatalytic performance. YbfF displays a high level of activity toward IPG butyrate and IPG caprylate and prefers the R-enantiomer of these substrates, producing the S-enantiomer of the IPG product with high enantiomeric excess (72 to 94% ee). The enantioselectivity of YbfF for IPG caprylate (E = 40) could be significantly enhanced when using dimethylformamide (DMF) or dimethyl sulfoxide (DMSO) as cosolvents in kinetic resolution experiments. The enzyme also shows high enantioselectivity toward 1-phenylethyl acetate (E ≥ 200), giving the chiral product (R)-1-phenylethanol with >99% ee. The high activity and enantioselectivity of YbfF make it an attractive enzyme for organic synthesis.     

1,2-Diphenoxiethane salts as potent antiplasmodial agents

In this article we present a series of non-cytotoxic potent human choline kinase (CK) inhibitors that exhibit nanomolar antiplasmodial activity in vitro. The most active antiplasmodial compounds, 10a–b, bearing a pyridinium cationic head were inactive against CK, while compounds 10g and 10j with a quinolinium moiety exhibit moderate inhibition of both the parasite and the enzyme. The results point towards an additional mechanism of action unrelated to CK inhibition that remains to be established.     

Purification and Properties of Catechol 1,2-Dioxygenase from Rhizobium leguminosarum biovar viceae USDA 2370

The catechol 1,2-dioxygenase of Rhizobium leguminosarum biovar viceae USDA 2370 was purified 296-fold, yielding a homogeneous preparation with a specific activity of 51.1 U mg of protein^-1. The molecular weight of the native protein was 70,000, with two identical subunits of 34,500 and 1 g-atom of iron per mol. The optimum pH for catalytic activity was 9.0 to 9.5.     

Synthesis,antimalarial activities and cytotoxicities of amino-artemisinin-1,2-disubstituted ferrocene hybrids

Artemisinin-ferrocene conjugates incorporating a 1,2-disubstituted ferrocene analogous to that embedded in ferroquine but attached via a piperazine linker to C10 of the artemisinin were prepared from the piperazine artemisinin derivative, and activities were evaluated against asexual blood stages of chloroquine (CQ) sensitive NF54 and CQ resistant K1 and W2 strains of Plasmodium falciparum (Pf). The most active was the morpholino derivative 5 with IC₅₀ of 0.86?nM against Pf K1 and 1.4?nM against Pf W2. The resistance indices were superior to those of current clinical artemisinins. Notably, the compounds were active against Pf NF54 early and late blood stage gametocytes – these exerted >86% inhibition at 1?µM against both stages; they are thus appreciably more active than methylene blue (～57% inhibition at 1?µM) against late stage gametocytes. The data portends transmission blocking activity. Cytotoxicity was determined against human embryonic kidney cells (Hek293), while human malignant melanoma cells (A375) were used to assess their antitumor activity.     

1,2-O-cyanoalkylidene derivatives of furanoses as 1,2-trans-glycosylating agents

Treatment of acetylated l-arabinofuranose, d-galactofuranose, and d-glucofuranose with trimethylsilyl cyanide in acetonitrile in the presence of stannous chloride gave the respective 1,2-O-(1-cyanoethylidene) derivatives. Triphenyl-methylium perchlorate-catalysed glycosylation of trityl ethers of monosaccharides by the above cyanoethylidene derivatives and by 3,5-di-O-benzoyl-1,2-O-(α-cyanobenzylidene)-β-l-arabinofuranose gave high yields of protected disaccharides containing a 1,2-trans-glycofuranosidic bond.     

Synthesis and cytokinin-like activity of 7-chloro-imidazo[1,2-c]pyrimidines

Some 5-amino substituted 7-chloro-imidazo[1,2-c]pyrimidines and 7-chloro-8-methylthio-imidazo[1,2-c]pyrimidines were synthesized for further information on the role of the purine ring in cytokinin structure/activity relationships. Their cytokinin-like activity was examined using four different tests: expansion of cucumber etiolated cotyledons; formation of chlorophyll in etiolated cotyledons of cucumber; preservation of chlorophyll breakdown in sections of barley leaves; inhibition of root growth in intact wheat seedlings. Compounds with the imidazopyrimidine ring were generally less active than those with the purine ring, with the exception of the pentenylamino derivatives, which showed an activity comparable with that of the control, kinetin.     

Circular dichroism of catechol 1,2-dioxygenase from Acinetobacter calcoaceticus

Circular dichroism (CD) spectra of catechol 1,2-dioxygenase from Acinetobacter calcoaceticus exhibit three positive ellipticity bands between 240 and 300 nm (250, 283, and 292 nm), two negative bands at 327 and 480 nm, and a low-intensity positive band at 390 nm. The fractions of helix β-form, and unordered form of the enzyme are 8, 38, and 54%, respectively. The circular dichroic bands at 327 and 480 nm and a part of the positive bands at 292 and 390 nm are associated with enzyme activity. Significant changes in absorption and CD spectra of the enzyme were observed when the temperature of the enzyme preparation was increased to 47°C, coinciding with the sharp decrease in enzyme activity observed at this temperature.     

Discovery of imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors

The synthesis and structure–activity relationships (SAR) of novel, potent imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors are described. The X-ray crystal structure of imidazo[1,2-a]pyrazine Aurora inhibitor 1j is disclosed. Compound 10i was identified as lead compound with a promising overall profile.     

Extradiol Cleavage of 3-Methylcatechol by Catechol 1,2-Dioxygenase from Various Microorganisms

The isofunctional enzymes of catechol 1,2-dioxygenase from species of Acinetobacter, Pseudomonas, Nocardia, Alcaligenes, and Corynebacterium oxidize 3-methylcatechol according to both the intradiol and extradiol cleavage patterns. However, the enzyme preparations from Brevibacterium and Arthrobacter have only the intradiol cleavage activity. Comparison of substrate specificity among these isofunctional dioxygenases shows striking differences in the oxidation of 3-methylcatechol, 4-methylcatechol and pyrogallol.     

Purification and characterisation of a gentisate 1,2-dioxygenase fromRalstonia solanacearum GMI 1000

The gene encoding gentisate 1,2-dioxygenase from a soil-borne Gram-negative bacterium,Ralstonia solanacearum GMI 1000, was cloned and overexpressed inEscherichia coli. The resulting product incorporated a (His) 6 tag was purified to homogeneity from the harvested cell extracts by affinity chromatography. SDS-PAGE showed that the polypeptide exhibited an approximate molecular mass of 38 kDa. The optimal temperature and pH for gentisate cleavage catalysed by the enzyme were 30 °C and 8.0, respectively. TheK _m of the enzyme was determined to be 56 μM. ThepI is 4.6–4.8. Moreover, site-directed mutagenesis revealed that His105, His 107, and His 146 are the crucial residues involved in the catalytic activity of gentisate 1,2-dioxygenase fromRalstonia solanacearum GMI 1000.     

Biological Process for Converting Naphthalene to cis-1,2-Dihydroxy-1,2-Dihydronaphthalene

A biological process for converting naphthalene to cis-1,2-dihydroxy-1,2-dihydronaphthalene (DHD) catalyzed by Pseudomonas putida strain 119 was optimized in flask experiments. These studies revealed the following: (i) P. putida 119 can propagate efficiently and produce DHD when supplied one of several carbon sources and naphthalene; (ii) maximum DHD production by P. putida 119 occurs in logarithmic-growth-phase cells and decreases at various rates in the stationary growth phase, depending upon the carbon source used; (iii) several analogs of salicylic acid can be used as effective inducers of naphthalene metabolism in P. putida cells growing on glucose; and (iv) the addition of chemical surfactants to naphthalene-cell (P. putida 119) mixtures stimulates DHD production.     

2-Phenylimidazo[1,2-b]pyridazine derivatives highly active against Haemonchus contortus

A series of 2-phenylimidazo[1,2-b]pyridazine derivatives were synthesized and evaluated for their in vitro anthelmintic activity against Haemonchus contortus. The most active compounds had in vitro LD₉₉ values of 30 nM, which is comparable to that of the benchmark commercial nematocide, Ivermectin.     

Synthesis and antibacterial activity of 7-(1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl) quinolones

A novel series of 7-(1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl) quinolones has been designed and synthesized in which the heterocyclic side chain is attached to the quinolone core through a carbon–carbon linkage. The antibacterial activity of the compounds was determined against a panel of Gram-positive and Gram-negative pathogens. Compounds 1b and 1e, bearing an 8-methoxy group as well as unsubstituted and (3S)-methyl substituted 1,2,3,4-tetrahydropyrrolo[1,2-a]pyrazin-7-yl side chains, respectively, demonstrated notable activity against ciprofloxacin-resistant clinical isolates of Streptococcus pneumoniae.     

Discovery of orally bioavailable imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors

We report a series of potent imidazo[1,2-a]pyrazine-based Aurora kinase inhibitors. Optimization of the solvent accessible 8-position led to improvements in both oral bioavailability and off-target kinase inhibition. Compound 25 demonstrates anti-tumor activity in an A2780 ovarian tumor xenograft model.     

Synthesis and structure activity relationship of imidazo[1,2-a]pyridine-8-carboxamides as a novel antimycobacterial lead series

Imidazo[1,2-a]pyridine-8-carboxamides as a novel antimycobacterial lead were generated by whole cell screening of a focused library against Mycobacterium tuberculosis. Herein, we describe the synthesis and structure activity relationship evaluation of this class of inhibitors and the optimization of physicochemical properties. These are selective inhibitors of Mycobacterium tuberculosis with no activity on either gram positive or gram negative pathogens.     

Loss of Homogentisate 1,2-Dioxygenase Activity in Bacillus anthracis Results in Accumulation of Protective Pigment

Melanin production is important to the pathogenicity and survival of some bacterial pathogens. In Bacillus anthracis, loss of hmgA, encoding homogentisate 1,2-dioxygenase, results in accumulation of a melanin-like pigment called pyomelanin. Pyomelanin is produced in the mutant as a byproduct of disrupted catabolism of L-tyrosine and L-phenylalanine. Accumulation of pyomelanin protects B. anthracis cells from UV damage but not from oxidative damage. Neither loss of hmgA nor accumulation of pyomelanin alter virulence gene expression, sporulation or germination. This is the first investigation of homogentisate 1,2-dioxygenase activity in the Gram-positive bacteria, and these results provide insight into a conserved aspect of bacterial physiology.     

Discovery of imidazo[1,2-a]pyridines as potent MCH1R antagonists

A series of imidazo[1,2-a]pyridine derivatives was identified and evaluated for MCH1R binding and antagonistic activity. Introduction of a methyl substituent at the 3-position of imidazo[1,2-a]pyridine provided compounds with a significant improvement in MCH1R affinity. Representative compounds in this series exhibited good potency and brain exposure in rats.