Studies on Reduced Extent Method for Inhibited Thermokinetics Of Enzyme－Catalyzed Reaction──Inhibition of the laccase－catalyzed oxidation of o－dihydroxybenzene by m－dihydroxybenzene

The thermokinetic reduced extent equations of reversible inhibitions for Michaiels-Menten enzymatic reaction were deduced, and then the criteria for distingushing inhibition type was given and the methods for calculating kinetic parameters, KM,Ki and Urn were suggested. This theory was applied to inverstigate the inhibited thermokinetics of laccase-catalyzed oxidation of o-dihydroxybenzene by m-dihydroxybenzene. The experimental results show the inhibition belongs to reversible competitive type, KM=6.224×10-3 mol L-1, Ki=2. 363 × 10-2 mol. L-1.

LCA studies for alkaline and enzyme catalyzed biodiesel production from palm oil

The life cycle analysis of biodiesel production from palm oil (PO) involves 3 stages: 1) Cultivation;2) Oil Extraction and 3) Transesterification of PO. There are several different approaches to the production process. The enzyme catalyzed process, was investigated and its environmental performance was compared with the conventional alkali-catalyzed process by using life cycle analysis (LCA). The enzyme catalyzed process is found to be technically a simpler production process and offers the production of less environmentally damaging wastes.

Analytical Solutions of System of Non-Linear Differential Equations in the Single-Enzyme, Single-Substrate Reaction with Non-Mechanism-Based Enzyme Inactivation

A closed form of an analytical expression of concentration in the single-enzyme, single-substrate system for the full range of enzyme activities has been derived. The time dependent analytical solution for substrate, enzyme-substrate complex and product concentrations are presented by solving system of non-linear differential equation. We employ He’s Homotopy perturbation method to solve the coupled non-linear differential equations containing a non-linear term related to basic enzymatic reaction. The time dependent simple analytical expressions for substrate, enzyme-substrate and free enzyme concentrations have been derived in terms of dimensionless reaction diffusion parameters ε, λ1, λ2 and λ3 using perturbation method. The numerical solution of the problem is also reported using SCILAB software program. The analytical results are compared with our numerical results. An excellent agreement with simulation data is noted. The obtained results are valid for the whole solution domain.

Pd-catalyzed sequential reaction for the synthesis of fused tricyclic compounds containing a dihydrofuran or isobenzofuranone unit

A novel Pd-catalyzed sequential reaction for the synthesis of fused tricyclic compounds with a dihydrofuran or isobenzofuranone unit was developed.

Novel Stereoselective Synthesis of 1,3-Dienyl Tellurides by Palladium Catalyzed Cross-coupling Reaction of (E)-β--Bromovinyl Tellurides

β-Bromovinyl tellurides are new difuctional reagents which undergo palladium-catalyzed cross-coupling reaction with alkenes to give conjugated dienyl tellurides.

Enzyme Kinetic Equations of Irreversible and Reversible Reactions in Metabolism

This paper compares the irreversible and reversible rate equations from several uni-uni kinetic mechanisms (Michaelis-Menten, Hill and Adair equations) and bi-bi mechanisms (single- and double- displacement equations). In reversible reactions, Haldane relationship is considered to be identical for all mechanisms considered and reversible equations can be also obtained from this rela- tionship. Some reversible reactions of the metabolism are also presented, with their equilibrium constant.

DIELS-ALDER REACTIONS OF FURAN WITH DIENOPHILES CATALYZED BY YbCl_3 Zi Niu ZHOU and Qi SHEN

The yield and stereoselectivity of the Diels-Alder reactions between furan(or 2-methylfuran)and different dienophiles are markedly enhanced by the catalysis of anhydrous YbCl_3.

Kinetics of Reaction of Bromo-epoxy Resin with Oleic Acid catalyzed by Dimethyl benzyl amine

The kinetics of reaction of bromo-epoxy resin with oleic acid in the presence of dimethylbenzylamine catalyst was studied. The reaction is a zero order reaction with respect to oleic acid, first order with respect to epoxy group and 0. 74 order with respect to dimethylbenzylamine. The reaction rate constants at various temperatures and activation energy were determined. The mechanism of this reaction was discussed. Keywords Tetrabromobisphenol-A, Bromo-epoxy resin, Oleic acid kinetics, Reaction mechanism

SYNTHESIS OF FUNCTIONAL MACROMOLECULE INTERMEDIATE THROUGH COUPLING REACTION CATALYZED BY [bmim]Cl/FeCl_3 IONIC LIQUID

To obtain new functional aromatic polymer material, 3,3’-biacenaphthene, which is used as macromolecule intermediate of function aromatic polymer material, was synthesized through the coupling reaction of acenaphthene catalyzing by ionic liquid ([bmim]Cl/FeCl3) at mild reaction condition. Pure 3,3’-biacenaphthene was obtained by recrystalling and column chromatography from the reaction mixture and was determined by GC/MS, 1HNMR and FTIR analysis. The influence of various reaction conditions on the yield of 3,3’-biacenaphthene were studied by GC analysis. The result shows that the optimum synthesis conditions of the coupling reaction are as following: the molar ratio of FeCl3 to [Bmim]Cl being 3, the mole ratio of FeCl3 in [Bmim]Cl/FeCl3 to acenaphthene being 4, the reaction temperature being 20 ℃, the reaction time being 4h and the solvent of the reaction system being PhNO2. Under those conditions, the yield of the 3,3’-biacenaphthene will be 48.71 % and selectivity of that will be 78.56 %. Further more, [bmim]Cl/FeCl3 has no pollution to environments and can be reused.

Facilitation of cascade biocatalysis by artificial multi-enzyme complexes——A review

Multi-enzyme complexes are the results of natural evolution to facilitate cascade biocatalysis.Through enzyme colocalization within a complex,the transfer efficiency of reaction intermediates between adjacent cascade enzymes can be promoted,resulting in enhanced overall reaction efficiency.Inspired by nature,a variety of approaches have been developed for the assembly of artificial multi-enzyme complexes with different spatial organizations,aiming at improving the catalytic efficiency of enzyme cascade.A recent trend of this research area is the creation of enzyme complexes with a controllable spatial organization which helps with the mechanistic studies and bears the potential to further increase metabolic productivity.In this review,we summarize versatile strategies for the assembly of artificial multi-enzyme complexes,followed by an inspection of the mechanistic studies of artificial multi-enzyme complexes for their enhancement of catalytic efficiency.Furthermore,we provide some highlighted in vivo,ex vivo,and in vitro examples that demonstrate the ability of artificial multi-enzyme complexes for enhancing the overall production efficiency of value-added compounds.Recent research progress has revealed the great biotechnological potential of artificial multi-enzyme complexes as a powerful tool for biomanufacturing.

Microcalorimetric Study on Tyrosine Oxidation Catalyzed by Tyrosinase

Through the method of initial heat release rate, the kinetic property of tyrosine oxidation catalyzed by tyrosinase from Pseudomonas maltophilia was investigated using a LKB-2107 batch microcalorimeter. Tyrosine was catalyzed and oxidized into L-dopa, then into melanin catalyzed by tyrosinase. We found that the tyrosinase reaction obeyed the Michaelis-Menten kinetics, and at 298.15K and pH 7.0, the initial exothermic rate (W0 ) are in the range of 0.1567~0.5704 mJ·s-1, the maximum exothermic rate (Wmax) are in 0.4152 ~ 0.8143mol·L-1, and mean value of the Michaelis constant (Km) is 2.199±0.105104 mol·L-1.

Demethylation of tumor necrosis factor-α converting enzyme promoter associated with high hepatitis B e antigen level in chronic hepatitis B

AIM: To evaluate tumor necrosis factor-α converting enzyme(TACE) methylation status in patients with chronic hepatitis B(CHB).METHODS: Eighty patients with hepatitis B e antigen(HBe Ag)-positive CHB, 80 with HBe Ag-negative CHB, and 40 healthy controls(HCs) were randomly enrolled in this study. Genomic DNA was extracted from peripheral blood mononuclear cells and methylation status of TACE promoter was determined by methylation-specific polymerase chain reaction. The clinical and laboratory parameters were collected.RESULTS: One hundred and thirty of 160 patients with CHB(81.25%) and 38 of 40 HCs(95%) displayed TACE promoter methylation. The difference was significant(χ2 = 4.501, P < 0.05). TACE promoter methylation frequency in HBe Ag-positive CHB(58/80, 72.5%) was significantly lower than that in HBe Ag-negative CHB(72/80, 90%; χ2 = 8.041, P < 0.01) and HCs(χ2 = 8.438, P < 0.01). However, no significant difference was observed in the methylation frequency between HBe Agnegative CHB and HCs(χ2 = 0.873, P > 0.05). In the HBe Ag-positive group, TACE methylation frequency was significantly negatively correlated with HBe Ag(r =-0.602, P < 0.01), alanine aminotransferase(r =-0.461, P < 0.01) and aspartate aminotransferase(r =-0.329, P < 0.01). CONCLUSION: Patients with HBe Ag-positive CHB have aberrant demethylation of the TACE promoter, which may potentially serve as a biomarker for HBe Ag seroconversion.

Unveiling enzyme-mimetic active intermediate of a bioinspired oxo-MoS_(x) electrocatalyst for aqueous nitrate reduction

Excessive nitrate in groundwater has emerged as a serious environmental concern. The elevated nitrate concentration in drinking water causes a serious threat to public health on account of the possible transformation of nitrate to nitrite, which is one of the main predisposing factors of methemoglobinemia [1].

Analytical expressions of the concentrations of substrate and product in enzyme inhibition process

The initial and boundary value problem in enzyme reactions mechanism for inhabitation process is discussed. Approximate analytical expressions for the concentrations of substrate and product are presented. Approximate analytical solutions of non-linear reaction equations containing non-linear terms related to enzymatic reaction mechanism are solved using Homotopy perturbation method. The relevant analytical expression for the substrate and product concentration profiles is discussed in terms of dimensionless reaction diffusion parameters α, β, γE, and γS. Numerical solution is also obtained using Matlab program. Our analytical expression compared with numerical estimation and good agreement is noted.

Adapting the usage of enzyme unit to its definition

The enzyme unit U,by its definition,is the amount of enzyme that catalyses the transformation of one micromole of substrate per minute under standard assay conditions.However,in practical use,it is identical with micromole or microgram per minute,which deviates from the essence of the definition as a measure of amount of substance.Such usage appears in many publications that involve enzyme kinetics and conveys obscure signification.In this article,we solved the confusion by regarding the unit U as a measure of amount of enzyme having a specified catalytic activity just like the basic SI unit mole(symbol mol) defined as the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of carbon 12.We introduced the concept of unit rate,ru,which is defined as the rate of a reaction mediated by 1 U enzyme,in calculating the enzyme units in an amount of enzyme so as to avoid the inconsistence of the expression with the definition of enzyme unit.The method can also be applied to the case of katal,the recommended SI unit of enzyme activity.

Theoretical Analysis of Immobilized Oxidase Enzyme Electrode in the Presence of Two Oxidants

In this paper, mathematical model of Martens and Hall (Analytical chemistry 66, 2763-2770 (1994)) for an immobilized oxidase enzyme electrode is discussed. The model involves the system of non-linear reaction diffusion equations under the steady state conditions. A simple and closed-form of approximate analytical expressions for the concentrations of the immobilization of three enzyme substrates has been derived by solving the system of non-linear reaction diffusion equations using new approach of homotopy perturbation method. Approximate polynomial expression of concentration of substrate, oxygen and oxidized mediator and current was obtained in terms of the Thiele moduli and the small values of parameters Bs, Bo and Bm (normalized surface concentration of substrate, oxygen and oxidized mediator). Furthermore, in this work the numerical simulation of the problem is also reported using Matlab program. An agreement between analytical expressions and numerical results is noted.