Effect of Static Magnetic Field on α-Amylase Activity and Enzymatic Reaction

The effect of magnetic field on a-amylase was studied. Under the experimental conditions, a-amylase solution was treated by 0.15 T, 0.30 T and 0.45 T static magnetic fields for a known period of time, then the activity, kinetic parameters, and the secondary conformation were investigated. The results showed that there was a considerable effect of the magnetic exposure on the α-amylase. The activity was increased by 27%, 34.1%, 37.8% compared with the control. It was also found that both kinetic parameters Km and Vm could be decreased due to the increasing magnetic field, Km decreased from 2.20×10^2 to 0.87×10^2, whereas Vm decreased from 2.0×10^3 g/min to 1.1 ×10^3 g/min. At the same time, there were some irregular changes in a-amylase secondary conformation.

Preparation of cross-linked enzyme aggregates of nitrile hydratase ES-NHT-118 from E.coli by macromolecular cross-linking agent

Cross-linked enzyme aggregates(CLEAs) of nitrile hydratase(NHase) ES-NHT-118 from Escherichia coli were prepared by using ammonium sulfate as precipitating agent followed by cross-linking with dextran polyaldehyde for the first time. In this process, egg white was added as protein feeder for facilitating the formation of CLEAs. The optimal conditions of the immobilization process were determined. Michaelis constants(Km) of free NHase and NHase CLEAs were also determined. The NHase CLEAs exhibited increased stability at varied pH and temperature conditions compared to its free counterpart. When exposed to high concentrations of acrylamide, NHase CLEAs also exhibited effective catalytic activity.

Morphological and kinetic parameters of the absorption of nitrogen forms for selection of Eucalyptus clones

Eucalyptus clones are selected according to productivity,wood quality,rooting capacity,and resistance to drought,frost and diseases.However,kinetic and morphological parameters that determine the absorption efficiency of nutrients such as nitrate(NO_(3)^(-)) and ammonium(NH_(4)^(+))are often not considered in breeding programs.The objective of this study was to evaluate the morphological,physiological and kinetic parameters of nitrogen uptake by clones of Eucalyptus saligna(32,864) and Eucalyptus grandis(GPC23).Morphological parameters in shoot and root systems,biomass and N concentrations in different organs,photosynthetic pigment concentrations,parameters of chlorophyll a fluorescence and photosynthetic rates were evaluated.Kinetic parameters,maximum absorption velocity(V_(max)),Michaelis-Menten constant(K_(m)),minimum concentration(C_(min)) and influx(I) were calculated for NO_(3)^(-)and NH_(4)^(+) in the two clones.E.granais clone was more efficient in the uptake of NO_(3)^(-)and NH_(4)^(+),and showed lower K_(m) and C_(min)values,allowing for the absorption of nitrogen at low concentrations due to the high affinity of the absorption sites of clone roots to NO_(3)^(-)and NH_(4)^(+).Higher root lengths,area and volume helped the E.grandis clone in absorption efficiency and consequently,resulted in higher root and shoot biomass.The E.saligna clone had higher K_(m) and Cmin for NO_(3)^(-)and NH_(4)^(+),indicating adaptation to environments with higher N availability.The results of NO_(3)^(-)and NH_(4)^(+) kinetic parameters indicate that they can be used in Eucalyptus clone selection and breeding programs as they can predict the ability of clones to absorb NO_(3)^(-)and NH_(4)^(+) at different concentrations.

Phosphomonoesterase Activities,Kinetics and Thermodynamics in a Paddy Soil After Receiving Swine Manure for Six Years

Soil phosphomonoesterase plays a critical role in controlling phosphorus(P) cycling for crop nutrition,especially in P-deficient soils.A 6-year field experiment was conducted to evaluate soil phosphomonoesterase activities,kinetics and thermodynamics during rice growth stages after consistent swine manure application,to understand the impacts of swine manure amendment rates on soil chemical and enzymatic properties,and to investigate the correlations between soil enzymatic and chemical variables.The experiment was set out in a randomized complete block design with three replicates and five treatments including three swine manure rates(26,39,and 52 kg P ha^(-1),representing low,middle,and high application rates,respectively) and two controls(no-fertilizer and superphosphate at 26 kg P ha^(-1)).The results indicated that the grain yield and soil chemical properties were significantly improved with the application of P-based swine manure from 0 to 39 kg P ha^(-1);however,the differences between the 39(M_(39)) and 52 kg P ha^(-1) treatments(M_(52)) were not significant.The enzymatic property analysis indicated that acid phosphomonoesterase was the predominant phosphomonoesterase in the tested soil.The M_(39) and M_(52) treatments had relatively high initial velocity(V_0),maximal velocity(V_(max)),and activation grade(lgN_a) but low Michaelis constant(K_m),temperature coefficient(Q_(10)),activation energy(E_a),and activation enthalpy(ΔH),implying that the M_(39) and M_(52) treatments could stimulate the enzyme-catalyzed reactions more easily than all other treatments.The correlation analysis showed that the distribution of soil phosphomonoesterase activities mainly followed the distributions of total C and total N.Based on these results,39 kg P ha^(-1) could be recommended as the most appropriate rate of swine manure amendment.