Peroxidase catalytic properties

Correct answer = B. Cellular damage is directly related to decreased ability of the cell to regenerate reduced glutathione, for which large amounts of NADPH are needed. RBCs have plenty of glutathione peroxidase. Catalytic properties of glucose 6-phosphate dehydrogenase in liver and RBCs are very similar. 

It is important to compare the catalytic properties of Prussian blue with known hydrogen peroxide transducers. Table 13.2 presents the catalytic parameters, which are of major importance for analytical chemistry selectivity and catalytic activity. It is seen that platinum, which is still considered as the universal transducer, possesses rather low catalytic activity in both H202 oxidation and reduction. Moreover, it is nearly impossible to measure hydrogen peroxide by its reduction on platinum, because the rate of oxygen reduction is ten times higher. The situation is drastically improved in case of enzyme peroxidase electrodes. However, the absolute records of both catalytic activity... 

Heme peroxidases can be classified into two large superfamilies, and four additional small nonrelated families/superfamilies, the members of each sharing general structural features, described in this first section. Main structural details related to the catalytic properties of some of the most outstanding heme peroxidases with a potential as industrial biocatalysts will be described in the next sections of this chapter. 

Zederbauer M, Furtmuller PG, Brogioni S et al (2007) Heme to protein linkages in mammalian peroxidases impact on spectroscopic, redox and catalytic properties. Nat Prod Rep 24 571-584... 

The first step of peroxidase catalysis involves binding of the peroxide, usually H2C>2, to the heme iron atom to produce a ferric hydroperoxide intermediate [Fe(IE)-OOH]. Kinetic data identify an intermediate prior to Compound I whose formation can be saturated at higher peroxide concentrations. This elusive intermediate, labeled Compound 0, was first observed by Back and Van Wart in the reaction of HRP with H2O2 [14]. They reported that it had absorption maxima at 330 and 410 nm and assigned these spectral properties to the ferric hydroperoxide species [Fe(III)-OOH]. They subsequently detected transient intermediates with similar spectra in the reactions of HRP with alkyl and acyl peroxides [15]. However, other studies questioned whether the species with a split Soret absorption detected by Back and Van Wart was actually the ferric hydroperoxide [16-18], Computational prediction of the spectrum expected for Compound 0 supported the structure proposed by Baek and Van Wart for their intermediate, whereas intermediates observed by others with a conventional, unsplit Soret band may be complexes of ferric HRP with undeprotonated H2O2, that is [Fe(III)-HOOH] [19]. Furthermore, computational analysis of the peroxidase catalytic sequence suggests that the formation of Compound 0 is preceded by formation of an intermediate in which the undeprotonated peroxide is coordinated to the heme iron [20], Indeed, formation of the [Fe(III)-HOOH] complex may be required to make the peroxide sufficiently acidic to be deprotonated by the distal histidine residue in the peroxidase active site [21],... 

The different location of the radical in the two types of Compound I structure is relevant, as it causes differences in their spectroscopic properties and results in differential catalytic activities. These differences only apply to Compound I, as the spectroscopic and catalytic properties of Compound II, in which only the ferryl is retained (see below), are similar for all the peroxidases. 

Ugarova NN, Rozhkova GD, Berezin IV (1979) Chemical modification of the e-amino groups of lysine residues in horseradish peroxidase and its effect on the catalytic properties and thermostability of the enzyme. Biochim Biophys Acta 570 31 12... 

All the catalytic intermediates of the peroxidase catalytic cycle as well as CIII present characteristic spectroscopic properties, which provide invaluable information on the structure of the porphyrin and its ligands. Here we discuss the evidence regarding the structure of Compound III. 

Martinez MJ, Ruiz-Duenas FJ, Guillen F et al (1996) Purification and catalytic properties of two manganese peroxidase isoenzymes from Pleurotus eryngii. Eur J Biochem 237 424—432... 

Kay E, Shannon LM, Lew JY (1967) Peroxidase isozymes from horseradish roots. II. Catalytic properties. J Biol Chem 242 2470-2473... 

Enzyme immunoassay (ElA) These assays exploit the catalytic properties of enzymes. Typically, antibodies labelled with an enzyme are used, for example horseradish peroxidase. The enzyme, which is bound and remains after washing, is able to convert added substrate to generate a coloured product that can be measured. The major enzyme immunoassay (ElA) is ELISA, which is covered in more detail later. 

Class III peroxidases have been the subject of numerous studies [10] and applications [11], since their extraordinary catalytic properties make them a valuable catalytic tool in the plant cell chemical factory, and in organic synthesis. In fact, class III peroxidases, together with other oxidative enzymes, such as cytochrome P450s and oxygenases [12], appear to be the main driving force in the evolution of plant metabolic pathways because individual enzymes can typically accept multiple substrates and form several products. This metabolic plasticity of class III peroxidases, paradoxically, has frequently led to misunderstanding of its vital function in the plant cell biochemical factory. 

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