Isolation and Characterization of 2,3-Dichloro-1-Propanol-Degrading Rhizobia

2,3-Dichloro-1-propanol is more chemically stable than its isomer, 1,3-dichloro-2-propanol, and is therefore more difficult to degrade. The isolation of bacteria capable of complete mineralization of 2,3-dichloro-1-propanol was successful only from enrichments at high pH. The bacteria thus isolated were found to be members of the α division of the Proteobacteria in the Rhizobium subdivision, most likely Agrobacterium sp. They could utilize both dihaloalcohol substrates and 2-chloropropionic acid. The growth of these strains in the presence of 2,3-dichloro-1-propanol was strongly affected by the pH and buffer strength of the medium. Under certain conditions, a ladder of four active dehalogenase bands could be visualized from this strain in activity gels. The enzyme involved in the complete mineralization of 2,3-dichloro-1-propanol was shown to have a native molecular weight of 114,000 and consisted of four subunits of similar molecular weights.     

Production of (R)-epichlorohydrin from 1,3-dichloro-2-propanol by two-step biocatalysis using haloalcohol dehalogenase and epoxide hydrolase in two-phase system

Recombinant Escherichia coli cells harbouring haloalcohol dehalogenase and epoxide hydrolase were successfully immobilized by adsorption onto perlite and used to prepare (R)-epichlorohydrin from 1,3-dichloro-2-propanol by two-step biocatalysis in a specially designed reactor. Two-phase solution was used as the reaction system in order to improve the yield of epichlorohydrin. In the two-phase system containing 40% (v/v) cyclohexane, the yield of racemic epichlorohydrin formed in the first step was 73%, and the yield of (R)-epichlorohydrin with enantiomeric excess (ee) ≥99% increased from 19.2% to 25.1% in the second step. Ultimately, the yield of (R)-epichlorohydrin reached 26.4% by optimization of the flow rate of air and amount of immobilized cells. To our knowledge, this was the first report on production of (R)-epichlorohydrin from 1,3-dichloro-2-propanol by two-step biocatalysis using haloalcohol dehalogenase and epoxide hydrolase.     

1,3-Dichloro-2-propanol induces apoptosis via both calcium and ROS in mouse melanoma cells

We demonstrated that the apoptotic cell death of mouse melanoma cells exposed to 1,3-dichloro-2-propanol (DCP) was Ca²⁺ dependent. 1,3-DCP inhibited the growth of mouse melanoma cells in a concentration-dependent manner. Furthermore, a terminal nick-end labeling of fragmented DNA (TUNEL) assay demonstrated that 1,3-DCP-induced apoptosis. Moreover, reactive oxygen species and Ca²⁺, generated by mouse melanoma cells that were exposed to 1,3-DCP, resulted in the activation of NF-κB and MAPKs. Finally, treatment with BAPTA, an intracellular Ca²⁺ chelator, completely inhibited the apoptosis that was induced by 1,3-DCP treatment of B16F10 cells.     

Kinetics of Bacterial Growth on Chlorinated Aliphatic Compounds

With the pure bacterial cultures Ancylobacter aquaticus AD20 and AD25, Xanthobacter autotrophicus GJ10, and Pseudomonas sp. strain AD1, Monod kinetics was observed during growth in chemostat cultures on 1,2-dichloroethane (AD20, AD25, and GJ10), 2-chloroethanol (AD20 and GJ10), and 1,3-dichloro-2-propanol (AD1). Both the Michaelis-Menten constants (K_m) of the first catabolic (dehalogenating) enzyme and the Monod half-saturation constants (K_s) followed the order 2-chloroethanol, 1,3-dichloro-2-propanol, epichlorohydrin, and 1,2-dichloroethane. The K_s values of strains GJ10, AD20, and AD25 for 1,2-dichloroethane were 260, 222, and 24 μM, respectively. The low K_s value of strain AD25 was correlated with a higher haloalkane dehalogenase content of this bacterium. The growth rates of strains AD20 and GJ10 in continuous cultures on 1,2-dichloroethane were higher than the rates predicted from the kinetics of the haloalkane dehalogenase and the concentration of the enzyme in the cells. The results indicate that the efficiency of chlorinated compound removal is indeed influenced by the kinetic properties and cellular content of the first catabolic enzyme. The cell envelope did not seem to act as a barrier for permeation of 1,2-dichloroethane.     

Purification and Characterization of Two Epoxide Hydrolases from Corynebacterium sp. Strain N-1074

Enzymes II_a and II_b, which catalyze the conversion of epichlorohydrin (ECH) to 3-chloro-1,2-propanediol (MCP), were purified from Corynebacterium sp. strain N-1074, which catalyzes the formation of (R)-MCP from prochiral 1,3-dichloro-2-propanol via ECH. The specific activity of enzyme II_a for the formation of MCP from ECH was about 6.4-fold higher than that of enzyme II_b. Both enzymes catalyzed the conversion of 1,2-epoxides to the corresponding diol, although they differed in several enzymatic properties.     

Purification and characterization of haloalcohol dehalogenase from Arthrobacter sp. strain AD2.

An enzyme capable of dehalogenating vicinal haloalcohols to their corresponding epoxides was purified from the 3-chloro-1,2-propanediol-utilizing bacterium Arthrobacter sp. strain AD2. The inducible haloalcohol dehalogenase converted 1,3-dichloro-2-propanol, 3-chloro-1,2-propanediol, 1-chloro-2-propanol, and their brominated analogs, 2-bromoethanol, as well as chloroacetone and 1,3-dichloroacetone. The enzyme possessed no activity for epichlorohydrin (3-chloro-1,2-epoxypropane) or 2,3-dichloro-1-propanol. The dehalogenase had a broad pH optimum at about 8.5 and a temperature optimum of 50 degrees C. The enzyme followed Michaelis-Menten kinetics, and the Km values for 1,3-dichloro-2-propanol and 3-chloro-1,2-propanediol were 8.5 and 48 mM, respectively. Chloroacetic acid was a competitive inhibitor, with a Ki of 0.50 mM. A subunit molecular mass of 29 kDa was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. With gel filtration, a molecular mass of 69 kDa was found, indicating that the native protein is a dimer. The amino acid composition and N-terminal amino acid sequence are given.     

Production of (R)-3-Chloro-1,2-Propanediol from Prochiral 1,3-Dichloro-2-Propanol by Corynebacterium sp. Strain N-1074

The production of (R)-3-chloro-1,2-propanediol [(R)-MCP] from prochiral 1,3-dichloro-2-propanol (DCP) was examined with a bacterial strain identified as a Corynebacterium strain. The addition of glycerol as a carbon source or some chlorinated alcohols to a medium was effective for the induction of activity catalyzing the transformation of DCP into MCP. The optimum pH for (R)-MCP production by the resting cell reaction was around 8.0. The optical purity of (R)-MCP formed was improved by keeping the level of DCP in the reaction mixture at a low concentration. (R)-MCP was obtained from 77.5 mM DCP with a 97.3% molar conversion yield and an 83.8% enantiomeric excess of its optical purity by periodic feeding of the substrate.     

Efficacies of Novel N-Halamine Disinfectants against Salmonella and Pseudomonas Species

Six novel N-halamine compounds of potential importance as disinfectants to the food-processing industry were tested against Salmonella enteritidis, Salmonella gallinarum, Salmonella typhimurium, and Pseudomonas fluorescens in aqueous solution. Inactivation times for 10⁶-fold reductions were determined as a function of water quality at pH 6.5 and 25°C. Phenol coefficients for the efficacies of the compounds against S. enteritidis have been reported also. When both stability and efficacy data are considered, as well as cost of production, two compounds, 1,3-dichloro-2,2,5,5-tetramethylimidazolidin-4-one and 1-chloro-2,2,5,5-tetramethylimidazolidin-4-one, offer the greatest potential as biocides for the food-processing industry.     

Enrichment of microbial cultures able to degrade 1,3-dichloro-2-propanol: a comparison between batch and continuous methods

Microbial cultures able to degrade xenobiotic compounds are the key element for biological treatment of waste effluents and are obtained from enrichment processes. In this study, two common enrichment methods, suspension batch and immobilized continuous, were compared. The main selection factor was the presence of 1,3-dichloro-2-propanol (1,3-DCP) as the single carbon source. Both methods have successfully enriched microbial consortia able to degrade 1,3-DCP. When tested in batch culture, the degradation rates of 1,3-DCP by the two consortia were different, with the consortia obtained by batch enrichment presenting slightly higher rates. A preliminary morphological and biochemical analysis of the predominant colonial types present in each degrading consortia revealed the presence of different constituting strains. Three bacterial isolates capable of degrading 1,3-DCP as single strains were obtained from the batch enrichments. These strains were classified by 16S rRNA analysis as belonging to the Rhizobiaceae group. Degradation rates of 1,3-DCP were lower when single species were used, reaching 45 mg l^-1 d^-1, as compared to 74 mg l^-1 d^-1 of the consortia enriched on the batch method. Mutualistic interactions may explain the better performance of the enriched consortia.     

Expression,characterization, and improvement of a newly cloned halohydrin dehalogenase from Agrobacterium tumefaciens and its application in production of epichlorohydrin

A gene encoding halohydrin dehalogenase (HHDH) from Agrobacterium tumefaciens CCTCC M 87071 was cloned and expressed in Escherichia coli. To increase activity and stability of HHDH, 14 amino acid residues around the active site and substrate-binding pocket based on the structural analysis and molecular docking were selected as targets for site-directed mutagenesis. The studies showed that the mutant HHDH (Mut-HHDH) enzyme had a more accessible substrate-binding pocket than the wild-type HHDH (Wt-HHDH). Molecular docking revealed that the distance between the substrate and active site was closer in mutant which improved the catalytic activity. The expressed Wt-HHDH and Mut-HHDH were purified and characterized using 1,3-dichloro-2-propanol (1,3-DCP) as substrates. The specific activity of the mutant was enhanced 26-fold and the value of k _cat was 18.4-fold as compared to the Wt-HHDH, respectively. The Mut-HHDH showed threefold extension of half-life at 45 °C than that of Wt-HHDH. Therefore it is possible to add 1,3-DCP concentration up to 100 mM and epichlorohydrin (ECH) was produced at a relatively high conversion and yield (59.6 %) using Mut-HHDH as catalyst. This Mut-HHDH could be a potential candidate for the upscale production of ECH.     

Opioid Peptides from Human β-Casein

A bacterium that assimilates 2,3-dichloro-1-propanol was isolated from soil by enrichment culture. The strain was identified as Pseudomonas sp. by the taxonomic studies. The strain converted 2,3-dichloro-1-propanol to 3-chloro-1,2-propanediol, releasing chloride ion. The conversion was stereospecific because the residual 2,3-dichloro-1-propanol and formed 3-chloro-1,2-propanediol gave optical rotation. The resting cells converted various halohydrins to the dehalogenated alcohols, and cell-free extracts had strong epoxyhydrolase activity. These results indicated that the strain assimilated 2,3-dichloro-1-propanol via 3-chloro-1,2-propanediol, glycidol, and glycerol. The possibility to manufacture optically active 2,3-dichloro-1-propanol is discussed.     

Purification and characterization of halohydrin hydrogen-halide lyase from a recombinant Escherichia coli containing the gene from a Corynebacterium sp.

Summary An enzyme catalyzing the interconversion of 1,3-dichloro-2-propanol (DCP) to epichlorohydrin (ECH) was purified from Escherichia coli JM109/ pST001, which carried the gene from Corynebacterium sp. N-1074. The enzyme was crystallized by the addition of ammonium sulphate. The enzyme had a relative molecular mass (M_r) of about 105 000 and consisted of four subunits identical in M_r (approx. 28 000). The enzyme catalysed both the transformation of various halohydrins into the corresponding epoxides with liberation of halide and its reverse reaction. These facts indicated that the enzyme was halohydrin hydrogen-halidelyase. Offprint requests to: T. Nagasawa     

The bacterial mutagenicity of nitropolychlorinated dibenzo-p-dioxins

The bacterial mutagenicity of 2-nitrodibenzo-p-dioxin, a mixture of 2-nitro-7-chloro- and 2-nitro-8-chlorodibenzo-p-dioxin, 7-nitro-2,3-dichloro-, 8-nitro-2,3,7-trichloro-, 2-nitro-1,3,7,8-tetrachloro- and 3-nitro-1,2,4,7,8-pentachlorodibenzo-p-dioxin was determined using Salmonella typhimurium tester strains TA98 and TA100 with and without rat hepatic S9 for metabolic activation. All the nitro-PCDDs exhibited some direct-acting mutagenicity with both tester strains, however, the activity was significantly lowered in the presence of exogenous S9 and the compounds were more mutagenic to tester strain TA98. The mutagenicity of the nitro-PCDDs was also dependent on structure because there was a marked decrease in activity with increasing chlorine content. Because nitro-PCDDs have recently been identified as incomplete combustion products of municipal waste, this study confirms that this new class of compounds contains some bacterial mutagens.     

Kinetic resolution of 1-chloro-3-(1-naphthyloxy)-2-propanol,an intermediate in the synthesis of beta-adrenergic receptor blockers

(R)- and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol are intermediates in the synthesis of β-adrenergic blocking agents and antihypertensive drugs such as propranolol and nadoxolol. Herein, improvement in the preparation of racemic 1-chloro-3-(1-naphthyloxy)-2-propanol generated from 1-naphthol and epichlorohydrin are reported. In addition, kinetic resolution studies have been conducted to obtain both (R) and (S)-1-chloro-3-(1-naphthyloxy)-2-propanol. These compounds were obtained in highly optically pure form by the stereoselective hydrolysis of its acyl derivatives using whole cell preparations containing enzymes from native sources. The results were compared with those obtained using commercial lipases.     

Synthesis and Biological Activity of Some Nucleoside Analogs of Hydroquinoline-3-Carbonitrile

Hydroquinoline acyclonucleosides 2, 4, 6a,b, 8a,b, 9a,b, and their corresponding N-alkyl derivatives (10–12) were obtained by the reaction of 1a,b with acetoxybutylbromide, (2-acetoxyethoxy)methyl bromide, 3-chloropropanol, 1,3-dichloro-2-propanol, epichlorohydrin, propargyl/allyl bromides in the presence of K₂CO₃ in dry dimethylformamide (DMF). In a similar manner, reaction of 1a,b with glycosyl/galactosyl and lactosyl bromide afforded the corresponding N-nucloside derivatives 13a,b, 15a,b, and 17, respectively. Deacetylation of the N-nucleosides derivatives in the presence of Et₃N/MeOH and few drops of water gave the deprotected derivatives 3, 5, 7a,b, 14a,b, 16a,b, and 18 in good yields, respectively. All the newly synthesized compounds are elucidated by infrared, ¹H, ¹³C NMR and elemental analyses. Some of these compounds were screened for antimicrobial activities.     

Enhanced biotransformation of 1,3-dichloro-2-propanol to epichlorohydrin via resin-based in situ product removal process

Biotransformation of 1,3-dichloro-2-propanol (DCP) to epichlorohydrin (ECH) by the whole cells of recombinant Escherichia coli expressing halohydrin dehalogenase was limited by product inhibition. To solve this problem and improve the ECH yield, a biotransformation strategy using resin-based in situ product removal (ISPR) was investigated. Seven macroporous resins were examined to adsorb ECH: resin HZD-9 was the best. When 10 % (w/v) HZD-9 was added to batch biotransformation, 53.3 mM ECH was obtained with a molar yield of 88.3 %. The supplement of the HZD-9 increased the ECH volumetric productivity from 0.5 to 2.8 mmol/l min compared to without addition of resin. In fed-batch biotransformation, this approach increased ECH from 31 to 87 mM. These results provide a promising basis for the biosynthesis of ECH.     

Preparation of (S)-2,3-dichloro-1-propanol byPseudomonas sp. and its use in the synthesis of (R)-epichlorohydrin

Summary Pseudomonas sp. OS-K-29 assimilated (R)-2,3-dichloro-1-propanol preferentially as the sole source of carbon. Isolation of optically pure (S)-2,3-dichloro-1-propanol with 100% enantiomer excess (e.e.) from the racemate was done based on this bacterial assimilation using immobilized-cells of OS-K-29 with calcium-alginate. The overall examination of the reactor involved 19 batches for 50 days without loss of its activity. Highly pure (R)-epichlorohydrin with 99.5% e.e. was prepared from the (S)-2,3-dichloro-1-propanol with treatment of aqueous NaOH. This new method is simple and useful for manufacturing optically active (S)-2,3-dichloro-1-propanol and (R)-epichlorohydrin.     

The biochemical toxicology of 1,3-difluoro-2-propanol,the major ingredient of the pesticide Gliftor: The potential of 4-methylpyrazole as an antidote

Administration to rats of 1,3-difluoro-2-propanol (100 mg kg⁻¹ body weight), the major ingredient of the pesticide gliftor, resulted in accumulation of citrate in the kidney after a 3 hour lag phase. 1,3-Difluro-2-propanol was found to be metabolized to 1,3-difluoroacetone and ultimately to the aconitate hydratase inhibitor (-) erythrofluorocitrate and free fluoride. The conversion of 1,3-difluoro-2-propanol to 1,3-difluoroacetone was found to be catalyzed by an NAD⁺-dependent alcohol dehydrogenase, while the defluorination was attributed to microsomal monooxygenase activity induced by phenobarbitone and inhibited by piperonyl butoxide. 4-Methylpyrazole was found to inhibit both of these processes in vitro and when administered (90 mg kg⁻¹ body weight) to rats, 2 hours prior to 1,3-difluoro-2-propanol, eliminated signs of poisoning, prevented (-) erythrofluorocitrate synthesis, and markedly decreased citrate and fluoride accumulation in vivo. 4-Methylpyrazole also appeared to diminish (-) erythrofluorocitrate synthesis from fluoroacetate in vivo, and this was attributed to its capacity to inhibit malate dehydrogenase activity. The antidotal potential of 4-methylpyrazole and the potential for 1,3-difluoro-2-propanol to replace fluoroacetate (compound 1080) as a vertebrate pesticide is discussed. © 1997 John Wiley & Sons, Inc. J Biochem Toxicol 12: 41–52, 1998     

Synthesis and antitubercular evaluation of novel substituted aryl and thiophenyl tethered dihydro-6H-quinolin-5-ones

A series of novel aryl and thiophenyl tethered dihydro-6H-quinolin-5-ones have been synthesized in very good yields through CeCl₃·7H₂O-NaI catalyzed one-pot condensation of β-enaminones derived from the respective methyl ketones; 1,3-cyclohexanedione & 5,5-dimethyl-1,3-cyclohexanedione and ammonium acetate refluxing in 2-propanol. Dihydro-6H-quinolin-5-ones 3a-f was further derivatized to the respective hydroxymethyl analogs using proline as an organocatalyst in aqueous media. Among the all 18 compounds screened for in vitro antimycobacterial activity against Mycobacterium tuberculosis H₃₇Rv (MTB), dihydro-6H-quinolin-5-ones 4e and 4f were found to be most active with MIC 3.13 μg/mL.     

Synthesis of 18F-labeled fluconazole and positron emission tomography studies in rabbits

[4-¹⁸F]2-(2,4-difluorophenyl)-1,3-bis(1H-1,2,4-triazol-1-yl)-2-propanol ([4-¹⁸F]fluconazole) was synthesized from its amino precursor. Fieldel-Crafts acylation of 3-fluoroacetanilide with chloroacetyl chloride produced 2′-fluoro-4′-acteamido-2-(1H-1,2,4-triazole-1-yl) acetophenone in 12% yield. Sequential reaction with (1) dimethylsulphoxonium methylide and (2) 1,2,4-triazole followed by in situ hydrolysis resulted in 2-(2-fluoro-4-aminophenyl)-1,3-bis(1H-1,2,4-triazol-l-yl)-2-propanol in 19% yield. A modified Schiemann reaction on this product resulted in [4-¹⁸F]fluconazole with a radiochemical yield of 1.0–2.0% (EOS) within 2 h. [4-¹⁸F]Fluconazole was used to measure the pharmacokinetics of fluconazole in rats by measurement of radioactivity in excised tissues and in rabbits by PET. In both species, there was rapid equilibration of [4-¹⁸F]fluconazole to a relatively uniform distribution of radioactivity in most organs.