Behavior Of Horseradish Peroxidase Research Articles

Catalytic and Inhibitory Kinetic Behavior of Horseradish Peroxidase on the Electrode Surface

Enzymatic biosensors are often used to detect trace levels of some specific substance. An alternative methodology is applied for enzymatic assays, in which the electrocatalytic kinetic behavior of enzymes is monitored by measuring the faradaic current for a variety of substrate and inhibitor concentrations. Here we examine a steady-state and pre-steady-state reduction of H2O2 on the horseradish peroxidase electrode. The results indicate the substrate-concentration dependence of the steady-state current strictly obeys Michaelis-Menten kinetics rules; in other cases there is ambiguity, whereby he inhibitor-concentration dependence of the steady-state current has a discontinuity under moderate concentration conditions. For pre-steady-state phases, both catalysis and inhibition show an abrupt change of the output current. These anomalous phenomena are universal and there might be an underlying biochemical or electrochemical rationale.

Studies on Electrocatalytically Kinetic Behavior of Horseradish Peroxidase at Salt Bridge Supported Bilayer Lipid Membrane

ABSTRACT This paper reports a novel and biological compatible biosensor that was used to study the electrochemical behavior of horseradish peroxidase (HRP) incorporated in salt bridge-supported bilayer lipid membrane (Sb-BLM). The incorporation of HRP was achieved by electrostatic interaction between HRP and LA anion sites pre-incorporated in Sb-BLM, which result in the enhancement of the electron exchange between the protein and the electrode surface. A quasi-reversible electron transfer of HRP was observed even in the absence of mediators. The electrocatalytically kinetic behavior of HRP and the electrode-kinetic process were investigated with this biosensor. In the presence of hydrogen peroxide, the electrocatalytical activity of HRP was determined.

Alteration of tight junctional permeability in the rat parotid gland after isoproterenol stimulation.

The permeability of junctional complexes to ultrastructural tracers of different molecular weight and the freeze-fracture appearance of junctional structure were investigated in the resting and stimulated rat parotid gland. Tracers were administered retrogradely via the main excretory duct, and allowed to flow by gravity (16 mmHg) into the gland for 15-60 min. Secretion was induced in some animals by intraperitoneal injection of isoproterenol. In resting glands, the tracers microperoxidase , cytochrome c, myoglobin, tyrosinase (subunits), and hemoglobin were restricted to the luminal space of the acini and ducts. In glands stimulated 1-4 h before tracer administration, reaction product for microperoxidase , cytochrome c, myoglobin, and tyrosinase was found in the intercellular and interstitial spaces, whereas hemoglobin was usually retained in the lumina. In contrast, horseradish peroxidase and lactoperoxidase appeared to penetrate the tight junctions and reaction product was localized in the extracellular spaces in both resting and stimulated glands. Diffuse cytoplasmic staining for horseradish peroxidase and lactoperoxidase was frequently observed in acinar and duct cells. The distribution of horseradish peroxidase was similar in both Sprague-Dawley and Wistar-Furth rats, and at concentrations of 0.1-10 mg/ml in the tracer solution. Freeze-fracture replicas of stimulated acinar cells revealed an increased irregularity of the tight junction meshwork, but no obvious gaps or discontinuities were observed. These findings indicate that (a) tight junctions in the resting rat parotid gland are impermeable to tracers of molecular weight greater than or equal to 1,900; (b) stimulation with isoproterenol results in a transient increase in junctional permeability allowing passage of tracers of molecular weight less than or equal to 34,500; (c) junctional permeability cannot be directly correlated with junctional structure; and (d) the behavior of horseradish peroxidase and lactoperoxidase in the rat parotid gland is inconsistent with their molecular weights. Cell membrane damage due to the enzymatic activity or binding of these two tracers may account for the observed distribution.

CORRECTION.The Behavior of Horseradish Peroxidase at High Hydrogen Peroxide Concentrations

ADVERTISEMENT RETURN TO ISSUEPREVArticleCORRECTION.The Behavior of Horseradish Peroxidase at High Hydrogen Peroxide ConcentrationsIra WeinrybCite this: Biochemistry 1966, 5, 8, 2776Publication Date (Print):August 1, 1966Publication History Published online1 May 2002Published inissue 1 August 1966https://doi.org/10.1021/bi00872a038RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (75 KB) Get e-Alerts Get e-Alerts