The asialoglycoprotein receptor (ASGPR) was used to mediate drug carrier for hepatic targeted drug delivery, this article showed the enzyme-catalyzed esterification of galactose and vinyl stearate and a kind of ASGPR ligand-targeted which was used to insert the surface of liposome has been synthesized. The structure of product has been confirmed by TLC, ESI-MS and 1H NMR. The factors of types and quantity of enzyme, organic solvents, molar ratio of substrate, temperature and time of reaction have been studied. Results showed when using acetone as reaction medium, the quantity of Novozym 435 immobilized lipase was 30 mg mL(-1), molar ratio of galactose to vinyl stearate was 1:5, and reacted at 60 degrees C for 12 h, the transformation of vinyl stearate reached more than 70%. This study provides a novel and efficient route to the synthesis of ligand-targeted modifier.
Acetone ; chemistry ; Asialoglycoprotein Receptor ; chemical synthesis ; Catalysis ; Esterification ; Galactose ; chemistry ; Ligands ; Lipase ; chemistry ; Stearates ; chemistry ; Temperature ; Vinyl Compounds ; chemistry

Biological synthesis of L-Ascorbyl Palmitate in organic system were studied in this text. The contradiction between conversion of vitamin C and concentration of L-Ascorbyl Palmitate were resolved. High conversion of vitamin C and concentration of L-Ascorbyl Palmitate were obtained by Novo435. A series of solvents(log P from -0.24 to 3.5 )were investigated for the reaction,and acetone was found to be the most suitable from the standpoint of the enzyme activity and solubility of L-ascorbic. And the equilibrium of the reaction was affected by the addition of the molecular sieves and temperature. Reaction carried out at 60 degrees C and with 20% 0.4nm molecular sieves is good for the enzyme to keep its activity and for making the equilibrium go to the product. With 1.094 g palmitic acid, 0.107 g vitamin C and 0.020 g Novo435, rotate rate of 200 r/min, the conversion of ascorbic reached 80% and the concentration of L-ascorbyl palmitate is 20 g/L after 48 h. Furthermore, reaction batch of Novo435 and substrates recycle were observed, the result indicated that Novo435 may used 4-5 times continuously with high conversion. And 6-O-unsaturated acyl L-ascorbates were synthesized through Novo435 condensation of ascorbic acid and various unsaturated fatty acids with high conversion in this text.
Ascorbic Acid ; analogs & derivatives ; biosynthesis ; Catalysis ; Enzymes, Immobilized ; chemistry ; metabolism ; Lipase ; chemistry ; metabolism

Lipases are widely used enzymes in biotechnology. Although they catalyze the same reaction, their sequences vary. Therefore, it is highly desired to develop a fast and reliable method to identify the types of lipases according to their sequences, or even just to confirm whether they are lipases or not. By proposing two scales based pseudo amino acid composition approaches to extract the features of the sequences, a powerful predictor based on k-nearest neighbor was introduced to address the problems. The overall success rates thus obtained by the 10-fold cross-validation test were shown as below: for predicting lipases and nonlipase, the success rates were 92.8%, 91.4% and 91.3%, respectively. For lipase types, the success rates were 92.3%, 90.3% and 89.7%, respectively. Among them, the Z scales based pseudo amino acid composition was the best, T scales was the second. They outperformed significantly than 6 other frequently used sequence feature extraction methods. The high success rates yielded for such a stringent dataset indicate predicting the types of lipases is feasible and the different scales pseudo amino acid composition might be a useful tool for extracting the features of protein sequences, or at lease can play a complementary role to many of the other existing approaches.
Amino Acids ; analysis ; chemistry ; Computational Biology ; Lipase ; chemistry ; classification ; Models, Chemical ; Sequence Analysis, Protein ; methods

Diacylglycerol, DAG, because of its multifunctional and nutritional properties, attracted considerable attention recently. Enzymatic synthesis of diacylglycerols from linoleic acid was investigated in a solvent-free reaction in a continuously operated fixed bed reactors containing Lipozyme RM IM. By appropriate manipulation of the fluid-residence time, the relative proportions of the various acylglycerols in the effluent stream can be controlled. In addition, the presence of excess glycerol is effective for the removal of water produced during the esterification reactions. Under the conditions of molar ratio of linoleic acid to glycerol of 0.5, the immoblized enzyme maintained high stability and allowed the reaction to continue for 10 days without significant deterioration in enzyme activity. It was determined that the conversion of fatty acid, content of 1,3-DAG and volume efficiency of reactor reached optima under the conditions: a packaged-bed reactor(with a ratio of packed length to inner diameter of 7.8), reacting temperature at 65 degrees C, molar ratio of linoleic acid to glycerol of 0.5, and feeding flow rate of 1.2 mL/min.
Catalysis ; Diglycerides ; chemical synthesis ; Enzyme Stability ; Enzymes, Immobilized ; chemistry ; Lipase ; chemistry

Proteus mirabilis lipase (PML) features tolerance to organic solvents and great potential for biodiesel synthesis. However, the thermal stability of the enzyme needs to be improved before it can be used industrially. Various computational design strategies are emerging methods for the modification of enzyme thermal stability. In this paper, the complementary algorithm-based ABACUS, PROSS, and FoldX were employed for positive selection of PML mutations, and their pairwise intersections were further subjected to negative selection by PSSM and G_REMLIN to narrow the mutation library. Thereby, 18 potential single-point mutants were screened out. According to experimental verification, 7 mutants had melting temperature (T_m) improved, and the ΔT_m of K208G and G206D was the highest, which was 3.75 ℃ and 3.21 ℃, respectively. Five mutants with activity higher than the wild type (WT) were selected for combination by greedy accumulation. Finally, the T_m of the five-point combination mutant M10 increased by 10.63 ℃, and the relative activity was 140% that of the WT. K208G and G206D exhibited certain epistasis during the combination, which made a major contribution to the improvement of the thermal stability of M10. Molecular dynamics simulation indicated that new forces were generated at and around the mutation sites, and the rearrangement of forces near G206D/K208G might stabilize the Ca²⁺ binding site which played a key role in the stabilization of PML. This study provides an efficient and user-friendly computational design scheme for the thermal stability modification of natural enzymes and lays a foundation for the modification of PML and the expansion of its industrial applications.
Enzyme Stability ; Lipase/chemistry* ; Molecular Dynamics Simulation ; Proteus mirabilis/metabolism* ; Solvents/chemistry*

We used adsorption method to immobilize the lipase by using nano-silica dioxide as the carrier. And we also studied different immobilization conditions effects on the catalytic activity. We got optimize immobilization conditions which were as follow the lipase quantity of 28,300 U/g, temperature of 45 degrees C, pH of 7.5 and treated for 10 h. Under these conditions the immobilized lipase activity yield 3867 U/g carrier. The best reactive temperature for immobilized lipase was 45 degrees C and higher than 5 degrees C for free enzyme, and the optimal pH dropped to 5.5 compared that of free enzyme (pH 7.0). The immobilized lipase stability for thermal and pH are improved than free lipase. When temperature was below 70 degrees C the immobilized enzyme activity was over 70% than initial activity. The free lipase activity just kept original 30% at 50 degrees C. When pH was 5-8, the immobilized lipase activity was still more than 50% and the free lipase only remained 20%. When we used the immobilized neutrophil lipase catalyzing different oil to produce biodiesel such as soybean oil, rapeseed oil and waste oil, the esterification rate of rapeseed oil was the highest.
Enzyme Stability ; Enzymes, Immobilized ; metabolism ; Hydrogen-Ion Concentration ; Lipase ; chemistry ; metabolism ; Metal Nanoparticles ; chemistry ; Silicon Dioxide ; chemistry ; Temperature

Lipase (EC3.1.1.3) from Candida sp. 99-125 was immobilized on chitosan by chemical covalence. Lipase was first immobilized to chitosan beads by activating its hydroxyl groups with carbodiimide followed by cross-linking more lipase to the amino groups with glutaraldehyde. In this article, different factors that influenced the immobilization were investigated, and the optimum conditions were ascertained. Comparative studies of organic solvent and thermal stability between free lipase and immobilized lipase were conducted. Immobilization enhanced the lipase stability against changes of temperature and organic solvent. Immobilization lipase can be reused in the synthesis system of palmitate hexadecyl. Operational stability tests indicated that the immobilized lipase occurs after 16 consecutive batches, the conversion rate remained 85%. Such results revealed good potential for recycling under esterification system.
Candida ; enzymology ; Carbodiimides ; chemistry ; Chitosan ; chemistry ; Cross-Linking Reagents ; Enzyme Stability ; Enzymes, Immobilized ; Lipase ; metabolism ; Palmitates ; chemistry

Our previous work has indicated that enzymatic resolution of glycidyl butyrate are strongly affected by many factors, including concentration of substrate, amount of lipase, the temperature, pH, shaking speed and reaction time. In this study, Plackett-Burman design was undertaken to evaluate the effects of the six factors. By regression analysis, concentration of substrate, amount of lipase and the temperature were found to be important for enzymatic resolution of glycidyl butyrate. In the second phase of the optimization process, a response surfacemethodology (RSM) was used to optimize the above critical factors, and to find out the optimal concentration levels and the relationships between these factors. By solving the quadratic regression model equation using appropriate statistic methods, the optimal parameter of the variables were determined as: 0.499 mol/L glycidyl butyrate, 30.23 mg/g lipase and 29.68 degrees C. In the optimum condition, the value of enantiomeric excess(ee%) was 93.28%. Compared to 84.65% which was the maximum ee% under the non-optimized condition, this study has a significant advancement. The experimental data under various conditions have validated the theoretical values.
Butyrates ; chemistry ; Catalysis ; Enzyme Activation ; Epoxy Compounds ; chemistry ; Lipase ; metabolism ; Molecular Conformation ; Propanols ; chemistry ; Regression Analysis ; Stereoisomerism ; Substrate Specificity ; Temperature

The lipase labeled with the fluorescein isothiocyanat (FITC) was immobilized on the derivatives of the polyethylene glycol. The article discussed the effect of factors on the characters of lipase and analyzed the relationships among the activity of lipase, conformation, and fluorescence spectrum while the activity and the fluorescence spectrum of immobilized lipase were determined. The results demonstrated that polyethylene glycol 400-diacrylate could form appropriate network to improve the activity of enzyme. Adding ligand induced the lipase's catalytic conformation to increase the activity twice more than before. The active centre of lipase could be released by the extraction of ligand thus increasing the activity. After immobilization, the stability of labeled lipase improved greatly: immobilized lipases retained more than 70% and 60% of initial activity under conditions of 90 degrees C and strong acid or alkali, respectively. After immersing immobilized lipases into guanidine hydrochloride or urea for 15 days, the lipases retained upwards of 70% activity. The fluorescence spectrum could obviously reflect the changes of the activity and conformation of lipase. The fluorescence intensity was the minimum in the optimal pH and temperature. In the denaturing agent it declined as time passed. These results indicated that the unfolded processes of immobilized lipases are different under different conditions.
Dextrans ; chemistry ; Enzyme Stability ; Enzymes, Immobilized ; chemistry ; metabolism ; Fluorescein-5-isothiocyanate ; analogs & derivatives ; chemistry ; Fluorescent Dyes ; chemistry ; Lipase ; chemistry ; metabolism ; Polyethylene Glycols ; chemistry ; Protein Unfolding ; drug effects

We investigated the transesterification of crude cottonseed oil with methyl acetate to biodiesel, by using Lipozyme TL IM and Novozym 435 as catalysts. Results showed that the biodiesel yield significantly increased with the addition of methanol into the reaction system, and the highest biodiesel yield of 91.83% was achieved with the optimum conditions as follows: n-hexane as solvent, molar ratio of methyl acetate to oil 9:1, 3% methanol based on the oil mass to inhibit the creation of acetic acid, 10% Lipozyme TL IM and 5% Novozym 435 as catalyst based on the oil mass, reaction temperature 55 degrees C and reaction time 8 h. Additionally, we explored the kinetics of lipase-catalyzed crude cottonseed oil to biodiesel, and proposed a kinetic model.
Acetates ; metabolism ; Biofuels ; analysis ; Catalysis ; Cottonseed Oil ; chemistry ; metabolism ; Enzymes, Immobilized ; metabolism ; Lipase ; metabolism