Effect of Additives on the Selectivity and Reactivity of Enzymes.

Enzymes have been widely used as efficient, eco-friendly, and biodegradable catalysts in organic chemistry due to their mild reaction conditions and high selectivity and efficiency. In recent years, the catalytic promiscuity of many enzymes in unnatural reactions has been revealed and studied by chemists and biochemists, which has expanded the application potential of enzymes. To enhance the selectivity and activity of enzymes in their natural or promiscuous reactions, many methods have been recommended, such as protein engineering, process engineering, and media engineering.

Enzymatic enantioselective aldol reactions of isatin derivatives with cyclic ketones under solvent-free conditions.

Nuclease p1 from Penicillium citrinum was observed to directly catalyze the asymmetric aldol reactions between isatin derivatives and cyclic ketones with high isolated yields (up to 95%) and moderate to good stereoselectivity (dr up to >99/1, ee up to 82%). A series of reaction conditions were investigated in detail, and the addition of deionized water had a big influence upon the enzyme activity. This case of biocatalytic promiscuity not only widens the applicability of nuclease p1 to new chemical transformation in organic synthesis, but also provides a potentially valuable method to construct pharmaceutically active compounds in medicinal chemistry.

Biocatalysts for cascade reaction: porcine pancreas lipase (PPL)-catalyzed synthesis of bis(indolyl)alkanes.

A cascade reaction between aldehydes and indole catalyzed by lipase from porcine pancreas Type II (PPL) in solvent mixture at 50 °C was reported for the first time. Some control experiments had been designed to demonstrate that the PPL was responsible for the cascade reaction. After the optimization of the stepwise process, a series of bis(indolyl)alkanes were prepared in moderate to excellent yields under the catalysis of PPL.

Unexpected three-component domino synthesis of pyridin-2-ones catalyzed by promiscuous acylase in non-aqueous solvent.

The Acylase "Amano" (AA)-catalyzed synthesis of valuable pyridin-2-ones via domino Knoevenagel condensation-Michael addition-intramolecular cyclization-oxidization reaction between aldehyde, cyanoacetamide and ethyl acetoacetate or cyclohexyl acetoacetate was developed in the sense of a one-pot strategy. Various aliphatic, aromatic and hetero-aromatic pyridin-2-ones could also be produced in the reaction. The mechanism was illustrated according to the controlled reaction, pyridin-2-one was formed via the oxidization by oxygen at the final step.

Reagentless biosensor based on layer-by-layer assembly of functional multiwall carbon nanotubes and enzyme-mediator biocomposite.

A simple and controllable layer-by-layer (LBL) assembly method was proposed for the construction of reagentless biosensors based on electrostatic interaction between functional multiwall carbon nanotubes (MWNTs) and enzyme-mediator biocomposites. The carboxylated MWNTs were wrapped with polycations poly(allylamine hydrochloride) (PAH) and the resulting PAH-MWNTs were well dispersed and positively charged. As a water-soluble dye methylene blue (MB) could mix well with horseradish peroxidase (HRP) to form a biocompatible and negatively-charged HRP-MB biocomposite.

A Combination of Computational and Experimental Approaches to Investigate the Binding Behavior of B.sub Lipase A Mutants with Substrate pNPP.

The formation of so-called enzyme-substrate complex is the key step for a successful enzyme-catalysis reaction. Enzymes use substrate-binding energy both to promote ground-state association and to stabilize the reaction transition state selectively. Some residues besides the catalytic triads play important roles toward the substrate binding process.

Integrating In Silico and In vitro approaches to dissect the stereoselectivity of Bacillus subtilis lipase A toward ketoprofen vinyl ester.

The asymmetric catalysis, as the character of enzyme, attracts increasing attention from the scientific and industrial communities. In this study, the Bacillus subtilis lipase A, as a model enzyme, is studied systematically to dissect its stereoselectivity toward (rac)-ketoprofen vinyl ester using a combination scheme of molecular docking and quantum mechanical/molecular mechanical (QM/MM) analysis. In this procedure, the rational orientation of the two enantiomers of ketoprofen vinyl ester is obtained with the AutoDock performing, and then, the steric contacts between the enzyme and substrate in the docking outputs are examined visually at the atomic level with a small-probe technique.

Multidrug nanoparticles based on novel random copolymer containing cytarabine and fluorodeoxyuridine.

Novel multidrug nanoparticles were self-assembled from the random copolymer containing cytarabine and fluorodeoxyuridine. The multidrug copolymer carrying 28.7wt.

Hydrolase-catalyzed fast Henry reaction of nitroalkanes and aldehydes in organic media.

Nitroalkanes underwent fast additions to a variety of structurally diverse aldehydes under the catalysis of d-aminoacylase in DMSO. The influences of reaction conditions including solvents, temperature, enzyme concentration and molar ratio of substrates were systematically investigated. Seventeen products were obtained in short time with moderate to high yields.

Enzymatic synthesis of amoxicillin via a one-pot enzymatic hydrolysis and condensation cascade process in the presence of organic co-solvents.

A cascade reaction combining the enzymatic hydrolysis of Penicillin G potassium salt (PGK) with the kinetically controlled enzymatic coupling of in situ formed 6-aminopenicillanic acid (6-APA) with p-hydroxyphenylglycine methyl ester (D-HPGM) to give amoxicillin as the final product by using a single enzyme has been demonstrated successfully. Ethylene glycol (EG) was employed as a component of reaction buffer to improve the synthesis yield. Reaction parameters, including different cosolvents, EG content, the loading of immobilized penicillin G acylase (IPA), and reaction temperature and time were studied to evaluate their effects on the reaction.

Facile synthesis of novel mutual derivatives of nucleosides and pyrimidines by regioselectively chemo-enzymatic protocol.

We established a facile regioselectively chemo-enzymatic synthesis procedure for the preparation of mutual derivatives of nucleosides and pyrimidines by sequential Markovnikov addition and acylation. Firstly, pyrimidine derivatives containing vinyl ester group were synthesized from pyrimidines and divinyl esters through Markovnikov addition catalyzed by K(2)CO(3) in DMSO at 80 degrees C, and the yields were ranged from 50% to 87%. Then regioselective acylation of ribavirin and cytarabine with pyrimidine vinyl ester was catalyzed by CAL-B (immobilized lipase from Candida antarctica) in anhydrous acetone.

Thermal treatment of galactose-branched polyelectrolyte microcapsules to improve drug delivery with reserved targetability.

A novel multilayered drug delivery system by LbL assembly of galactosylated polyelectrolyte, which is possible to have the potential in hepatic targeting by the presence of galactose residues at the microcapsule's surface, is designed. Thermal treatment was performed on the capsules and a dramatic thermal shrinkage up to 60% decrease of capsule diameter above 50 degrees C was observed. This thermal behavior was then used to manipulate drug loading capacity and release rate.

Hepatic-targeting microcapsules construction by self-assembly of bioactive galactose-branched polyelectrolyte for controlled drug release system.

We describe the construction of hepatic-targeting microcapsules by self-assembly of chemo-enzymatic synthesized poly(vinyl galactose ester-co-methacryloxyethyl trimethylammonium chloride) (PGEDMC) containing galactose branches, which can be specifically recognized by membrane bound galactose receptors (ASGPR), for acyclovir (ACV) controlled release system. Alternate deposition of PGEDMC and poly(sodium 4-styrenesulfonate) (PSS) was carried out on ACV microcrystals. It was revealed that the drug release rate decreases with the increase of coated layer number and a microcapsule-drying treatment would enhance the sustained release effect probably because of a multilayer shrink and tightness during the process.

Promiscuous zinc-dependent acylase-mediated carbon-carbon bond formation in organic media.

A zinc-dependent acylase, D-aminoacylase from Escherichia. Coli, displays a promiscuous activity to catalyze the carbon-carbon bond formation reaction of 1,3-dicarbonyl compounds to methyl vinyl ketone in organic media.

N-methylimidazole significantly improves lipase-catalysed acylation of ribavirin.

N-methylimidazole, a molecular solvent, but also, in cationic form, a component of 1-alkyl-3-methylimidazolium ([C(n)MIM]+) ionic liquids, showed promise as an additive in accelerating remarkably transesterification catalyzed by lipase acrylic resin from Candida antarctica (CAL-B).

Bioactive galactose-branched polyelectrolyte multilayers and microcapsules: self-assembly, characterization, and biospecific lectin adsorption.

We describe the fabrication of multilayers and microcapsules with biologically designed targeting activity using chemoenzymatic synthesized carbohydrate-branched polyelectrolytes. A novel cationic d-galactose-branched copolymer [poly(vinyl galactose ester-co-methacryloxyethyl trimethylammonium chloride), PGEDMC] is alternated with poly(styrene sulfonate) (PSS) to form thin multifilms by the layer-by-layer (LbL) technique on such different solid surfaces as quartz slides, poly(ethylene terephthalate) (PET) films, silicon wafers, and polystyrene (PS) microparticles. The experimental protocols were first optimized on flat, smooth silica substrates using UV-vis, contact angle, and atomic force microscopy (AFM) measurements.

Markedly enhancing lipase-catalyzed synthesis of nucleoside drugs' ester by using a mixture system containing organic solvents and ionic liquid.

Eightfold higher yields and three times faster reaction rates were achieved by means of using a mixture solvent system composed of 90% acetone and 10% [BMIM]BF4 in the lipase-catalyzed regioselective synthesis of polymerizable ester of nucleoside drugs.

Basic ionic liquid as catalysis and reaction medium: a novel and green protocol for the Markovnikov addition of N-heterocycles to vinyl esters, using a task-specific ionic liquid, [bmIm]OH.

A basic ionic liquid, 1-methyl-3-butylimidazolium hydroxide ([bmIm]OH), has been introduced as a catalyst and reaction medium for the Markovnikov addition of N-heterocycles to vinyl esters under mild conditions. The evidence for the role of this basic ionic liquid [bmIm]OH in promoting the Markovnikov addition has been given. On the basis of the evidence, a mechanism was postulated.

Controllable synthesis of polymerizable ester and amide prodrugs of acyclovir by enzyme in organic solvent.

A facile control of the acylation position at the primary hydroxyl and amino of acyclovir, respectively, was achieved and five polymerizable acyclovir prodrugs were synthesized. Various reaction conditions were studied in detail. Thus, lipase acrylic resin from Candida antarctica (CAL-B) in pyridine or acetone showed high chemo-selectivity toward the primary hydroxyl of acyclovir.

Chemo-enzymatic synthesis of raffinose-branched polyelectrolytes and self-assembly application in microcapsules.

A novel biocompatible polyelectrolyte poly(vinyl raffinose-co-acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe(2+)/K(2)S(2)O(8)/H(2)O(2) starting from enzymatically-synthesized monomer: 1-O-vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer-by-layer technique.

Controllable regioselective acylation of rutin catalyzed by enzymes in non-aqueous solvents.

An efficient route to synthesize 3''- and 4'''-vinyl rutin esters has been developed by enzyme-catalyzed regioselective acylation of rutin with divinyl dicarboxylates in organic media. Alkaline protease from Bacillus subtilis provided 3''-O-substituted vinyl rutin esters in pyridine, and Novozym 435 gave 4'''-O-substituted vinyl rutin esters in tert-butanol.

Hydrolase-catalyzed Michael addition of imidazoles to acrylic monomers in organic medium.

Hydrolase-catalyzed Michael addition of imidazole derivatives to acrylic monomers in organic medium was described. A serial of N-substituted imidazole derivatives were successfully synthesized in moderate yields by the catalysis of hydrolases in organic medium. Nine commercially available hydrolases from different sources were screened and all of them were found to be able to catalyze this type of addition reaction.

Regioselective enzymatic synthesis of non-steroidal anti-inflammatory drugs containing glucose in organic media.

Enzymatic transesterification of glucose with the vinyl ester of non-steroidal anti-inflammatory drugs (NSAIDs) was in organic media performed for synthesis of novel NSAIDs-glucose conjugates. Glucose was regioselectively acylated at the 6-hydroxyl group. The indomethacin-glucose conjugate and ketoprofen-glucose conjugate were produced by the catalysis of alkaline protease from Bacillus subtilis in the respective yields of 42% (over 48 h) and 63% (over 40 h).

Regioselective enzymatic acylation of ribavirin to give potential multifunctional derivatives.

Lipase-catalyzed synthesis of potential multifunctional ribavirin derivatives was performed in acetone. Divinyl dicarboxylates with different chain lengths (C4, C6, C9, C10) were used as acyl donors and the reactions were catalyzed by lipase immobilized on acrylic resin from Candida antarctica (CAL-B). Ribavirin was regioselectivly acylated at the primary hydroxyl groups and the corresponding vinyl esters (C4, C6, C9, C10) were prepared in respective yields of 48%, 65%, 54%, 55%.

Ultrasound-accelerated enzymatic synthesis of sugar esters in nonaqueous solvents.

Comparative studies of enzymatic synthesis of glucose esters under ultrasound and shaking were carried out in nonaqueous media. The influence of solvents, enzymes, chain length of the acyl donors, the power of the ultrasound bath, and intermittent ultrasound on the enzymatic synthesis was investigated. Among the eight solvents selected, pyridine was the most appropriate with alkaline protease from Bacillus subtilis whether under ultrasound or shaking.