About: Catalase is a(n) research topic. Over the lifetime, 15500 publication(s) have been published within this topic receiving 687971 citation(s).
Papers published on a yearly basis
Abstract: Publisher Summary Catalase exerts a dual function: (1) decomposition of H 2 O 2 to give H 2 O and O 2 (catalytic activity) and (2) oxidation of H donors, for example, methanol, ethanol, formic acid, phenols, with the consumption of 1 mol of peroxide (peroxide activity) The kinetics of catalase does not obey the normal pattern Measurements of enzyme activity at substrate saturation or determination of the K s is therefore impossible In contrast to reactions proceeding at substrate saturation, the enzymic decomposition of H 2 O 2 is a first-order reaction, the rate of which is always proportional to the peroxide concentration present Consequently, to avoid a rapid decrease in the initial rate of the reaction, the assay must be carried out with relatively low concentrations of H 2 O 2 (about 001 M) This chapter discusses the catalytic activity of catalase The method of choice for biological material, however, is ultraviolet (UV) spectrophotometry Titrimetric methods are suitable for comparative studies For large series of measurements, there are either simple screening tests, which give a quick indication of the approximative catalase activity, or automated methods
TL;DR: A quantitative, spectrophotometric technique for following the breakdown of hydrogen peroxide has been developed for routine studies of catalase kinetics and appears to give lower values forCatalase activity than do titration techniques.
Abstract: Several methods have been developed for following the breakdown of hydrogen peroxide catalyzed by catalase, but these either have not been sufficiently quantitative or have not proved rapid enough to yield reliable data during the critical 1st or 2nd minute of the reaction. Chemical procedures in which residual peroxide is titrated with permanganate (l-3) or an excess of permanganate is measured calorimetrically (4) are accurate except for reaction times of less than a minute, although Lemberg and Foulkes (5) developed a micromethod for obtaining data every 10 seconds (see also Ogura et al. (6)). Considerable variability is unavoidable, however, when samples must-be taken at such short intervals. The manometric method for measuring oxygen evolved from the system proved in detailed studies to be unsuited for following the rapid breakdown of peroxide in which a diffusion process across the liquid-air interface becomes limiting. This is manifested by changes in both the order of the reaction and the rate of evolution of oxygen with variations in the rate of agitation of the reaction mixture (7). Direct measurement of hydrogen peroxide by polarography provides good quantitative data during the 1st minute of the reaction which fit first order kinetics (8). However, an elaborate, special, electronic circuit is needed for such measurements. Furthermore, as pointed out by Bonmschen, Chance, and Theorell (8), this method appears to give lower values for catalase activity than do titration techniques. Preliminary experiments for following the breakdown of hydrogen peroxide by observing the decrease in light absorption of peroxide solutions in the ultraviolet were reported by Chance (9) and Chance and Herbert (10). The potentialities of this method have been investigated and a quantitative, spectrophotometric technique for following the breakdown of hydrogen peroxide has been developed for routine studies of catalase kinetics.
TL;DR: These low molecular mass antioxidant molecules add significantly to the defense provided by the enzymes superoxide dismutase, catalase and glutathione peroxidases, which are termed ‘oxidative stress’.
Abstract: An imbalance between oxidants and antioxidants in favour of the oxidants, potentially leading to damage, is termed 'oxidative stress'. Oxidants are formed as a normal product of aerobic metabolism but can be produced at elevated rates under pathophysiological conditions. Antioxidant defense involves several strategies, both enzymatic and non-enzymatic. In the lipid phase, tocopherols and carotenes as well as oxy-carotenoids are of interest, as are vitamin A and ubiquinols. In the aqueous phase, there are ascorbate, glutathione and other compounds. In addition to the cytosol, the nuclear and mitochondrial matrices and extracellular fluids are protected. Overall, these low molecular mass antioxidant molecules add significantly to the defense provided by the enzymes superoxide dismutase, catalase and glutathione peroxidases.
TL;DR: Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration and indirect measurements of the decrease of light absorption caused by the decomposition of hydrogen peroxide byCatalase.
Abstract: Publisher Summary This chapter discusses the assay of catalases and peroxidases are: (1) catalase assay by disappearance of peroxide; (2) method for crude cell extracts; (3) direct spectrophotometric assay of catalase and peroxidase in cells and tissues; and (4) peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products. Two methods are described for the catalase assay by disappearance of peroxide are: ultraviolet spectrophotometry and permanganate titration. Ultraviolet spectrophotometryis a method devised, on the basis of the absorption curves for peroxide solutions, for determining the activity of catalase by direct measurements of the decrease of light absorption in the region 230 to 250 mμ caused by the decomposition of hydrogen peroxide by catalase. In the case of method for crude cell extracts, oxygen evolution caused by the decomposition of hydrogen peroxide is measured with the conventional manometric technique. Peroxidase assay by spectrophotometric measurements of the disappearance of hydrogen donor or the appearance of their colored oxidation products includes the guaiacol test and the pyrogallol test.
TL;DR: The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen.
Abstract: The reactive superoxide radical, O2-, formerly of concern only to radiation chemists and radiobiologists, is now understood to be a normal product of the biological reduction of molecular oxygen. An unusual family of enzymes, the superoxide dismutases, protect against the deleterious actions of this radical by catalyzing its dismutation to hydrogen peroxide plus oxygen.