Conformation Of Horseradish Peroxidase Research Articles

Effects of dielectric barrier discharge cold plasma on the activity, structure and conformation of horseradish peroxidase (HRP) and on the activity of litchi peroxidase (POD)

Litchi is one kind of the precious tropical fruits, but it is easily affected by enzymatic browning resulting in great loss to farmers. In the present study, dielectric barrier discharge cold plasma was used to inactivate the litchi peroxidase (POD), one of the enzymes responsible for browning. Results indicated that after 10 min treatment, the residual activity of the POD extracted from pericarp decreased to 47.16%. The effect of cold plasma on POD structure was studied by using horseradish peroxidase (HRP) as a model enzyme. The HRP activity was decreased by about 85% after 180 s of treatment. UV and fluorescence spectral results suggested that the secondary and tertiary structures of HRP were changed through plasma treatment, hydrophobic aromatic amino acids and hemes were exposed and modified. Circular dichroism (CD) spectra indicated that after exposed to plasma for 180 s, the content of α-helix in HRP were decreased from 21.41% to 8.53%, and the β-sheet content raised from 23.29% to 32.11%. The presented study concluded that cold plasma is capable of reducing the activity of litchi POD, which will provide a new thought for prolonging shelf life of easy-browning fruits.

Conformation and activity alteration of horseradish peroxidase induced by the interaction with gene carrier polyethyleneimines

Polyethyleneimine (PEI) has long been considered as “golden standard” for polymeric gene delivery carriers. However the molecular basis of the cytotoxicity of PEI is poorly understood. Little is known about the effects of PEI on the structure and functions of biomacromolecules. In this work, fluorescence, UV–vis absorption, circular dichroism spectroscopy were conducted to investigate the influence of PEI of average molecular weight 25, 10 and 1.8kDa (denoted as PEI25k, PEI10k and PEI1.8k) on the conformation of horseradish peroxidase (HRP) and its catalytic efficiency. Zeta-potential measurement and isothermal titration calorimetry were used to reveal the mechanism of the interaction between PEIs and HRP. PEIs were found to bind onto the surface of HRP predominantly via hydrophobic interaction and hydrogen bond or van der Waals interaction. The complex formation between HRP and PEI induced a more compact conformation of the enzyme and an increased hydrophobicity of the microenvironment surrounding heme pocket. The conformational change of HRP had little impact on the affinity towards H2O2 and phenol. However, the increase in the non-planarity of porphyrin ring in the heme group led to an increase in the exposure degree of the active center and thus an enhancement of catalytic efficiency of HRP in the presence of high molecular weight PEIs (PEI25k and PEI10k). The polymer size played an important role in PEI-HRP interaction. PEI of low molecular weight (PEI1.8k) was less efficient to alter the conformation and catalytic activity of HRP in aqueous solutions.

Time Effect of Vacuum Treatment on Activity Index of Horseradish Peroxidase

The time effects of different vacuum treatment on the activity index (RZ=A403/A280) of the horseradish peroxidase (HRP) was investigated experimentally via the ultraviolet-visible spectroscopic techniques. The results have shown that Ultraviolet-Visible (UV-Vis) spectra have been changed obviously. Experimental results indicate that the conformation of HRP can be changed by vacuum. The activity index decrease possibly was caused by the conformation variations of HRP.

Study of High Voltage Electric Field on the Mechanism of Horseradish Peroxidase Activity

The activity of Horseradish Peroxidase (HRP) was enhanced with different strength of high voltage electric field. The results have shown that Ultraviolet-Visible spectra have been changed obviously. Experimental results indicate that the conformation of HRP can be changed by electric field. The study also showed that the activity index of HRP was increased by the certain strength of electric field. The activity index increase possibly was caused by the conformation variations of HRP. The result of this study has important meaning to explain the macroscopical electrostatic biological effects.

Inhibition mechanism of lanthanum ion on the activity of horseradish peroxidase in vitro

In order to understand the inhibition mechanism of lanthanum ion (La 3+) on the activity of horseradish peroxidase (HRP), the effects of La 3+ on the activity, electron transfer and conformation of HRP in vitro were investigated by using cyclic voltammetry (CV), atomic force microscopy (AFM), circular dichroism (CD), high performance liquid chromatography (HPLC), matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI-TOF/MS) and inductively coupled plasma mass spectrometry (ICP-MS). It was found that La 3+ can combine with the amide groups of the polypeptide chain in HRP molecule, forming the complex of La 3+ and HRP (La-HRP). The formation of the La-HRP complex causes the destruction of the native structure of HRP molecule, leading to the decrease in the non-planarity of the porphyrin ring in the heme group of HRP molecule, and then in the exposure extent of active center, Fe(III) of the porphyrin ring of HRP molecule. Thus, the direct electrochemical and catalytic activities of HRP are decreased. It is a possible inhibition mechanism of La 3+ on the activity of peroxidase.

Effects of different valences of cerium ion on conformation of Horseradish Peroxidase

Our previous studies demonstrated that Ce 4+ could induce reactive oxygen species (ROS) burst as a signal to promote pacilitaxel biosynthesis in suspension cultured Taxus cuspidate cells. To further understand the mechanism of cerium ions inducing ROS burst, circular dichroism (CD), synchronous fluorescence, and electron paramagnetic resonance (EPR) were used to detect them inducing conformational change of horseradish peroxidase (HRP). Horseradish peroxidase activity was reduced by 78% by 0.1 mmol/L Ce 4+, whereas it was only reduced by 28% by 0.1 mmol/L Ce 3+. Circular dichroism spectra showed that the percentage of transition from helical content and other structure to β strands and β turns was 23.1 when induced by Ce 4+, whereas it was only 13.2 when induced by Ce 3+. In synchronous fluorescence spectra, Ce 4+ led to red shift and intensity-elevation of tryptophan fluorescence emission maximum, whereas in the case of Ce 3+, the results were a contrast to the above. Furthermore, g factor ( g x and g y ) in electron paramagnetic resonance (EPR) induced by Ce 4+ and Ce 3+ was significantly different. These results indicated that the different valence of cerium ion induced various conformations of HRP, and Ce 4+ was more effective than Ce 3+. This suggested that Ce 4+ affected the burst of ROS through changing the conformation of oxidoreductase.