Peroxidase Japanese radish

Iron atoms in states other than Fe(II) and Fe(III) are rare in biological material, but there is one case where Mossbauer evidence has pointed to an Fe(IV) electronic configuration. Horseradish peroxidase, when it forms peroxide derivatives (Compounds I and II of HRP), displays an isomer shift which is about equal to that obtained with Fe metal (23). A similar observation has also been found on an analogous compound, Japanese Radish Peroxidase (72). There is no evidence for Fe(I) or Fe (IV) states in any other hemoproteins, or in any of the iron-sulfur proteins. 

Japanese radish peroxidase a 55 700f Ferriprotoporphyrin IX 28 Rhombic... 

The spectrum of CIII japanese radish peroxidase exhibits two widely splitted lines with a quadrupole splitting AEq = 2.37 mm s 1 and an isomer shift 8pe = 0.29 mm s 1 at 77°K [145], very similar to those observed in oxyhemoglobin [144], a horseradish peroxidase [146], The electronic structure of the iron is apparently determined by the Fe-C>2 bond with a marginal contribution of the fifth, axial ligand provided by the protein (Fig. 11.8). 

Fig. 11.8 Mossbauer absorption spectrum of Japanese radish peroxidase a-hydrogen peroxide Compound III at (a) 77°K and (b) 195°K. Reproduced with permission from [145]...

Mossbauer spectra has been extensively used to probe the structure of the iron nucleus in biological FeIV=0 compounds. These include horseradish peroxidase compoundl[134,180,181], horseradish peroxidase compound II [182,183], horseradish peroxidase compound X [181], Japanese-radish peroxidase compounds I and II [184], chloroperoxidase compound I [185], cytochrome c peroxidase compound I [186] and ferryl myoglobin [183]. Examples of Mossbauer spectra attributed to non-porphyrin-bound FeIV are only available from synthetic model compounds. These include compounds with [130] and without [4-8] an FeIV=0 bond. 

Ohya, T., Morimura, Y., Saji, H., Mihara, T., and Ikawa, T., 1997, Purification and characterisation of ascorbate peroxidase in roots of Japanese radish, Plant Science 125 137n 145. 

A titration study of a peroxidase from Japanese radish has been reported by Morita and Kameda (1958). The titration curves of native protein, acid-denatured protein, and alkali-denatured protein are dramatically different. Unfortunately only continuous titration curves were obtained, so that an interpretation of the data is not possible at this time. 

According to ORD measurements of ferric HRP and its apoprotein, splitting of the heme appears to cause a reduction of the estimated a-helix content (260, 259). CD spectra of Japanese-radish peroxidase a have been interpreted as reduction of about 35% (upper limit) in the a-helix content upon removal of the heme with possible formation of / -structure. Differences between the oxidized and reduced forms of this peroxidase have been recorded (261) [see above, Myoglobin and Hemoglobin, ultraviolet region],... 

The peroxidase enzyme, Japanese-radish peroxidase a (JRP-o), has been prepared with enriched Fe by combination of the apo-peroxidase with... 

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