Peroxidase physiological role

Gaspar, T. Penel, C. Thorpe, T Greppin, H. Peroxidases 1970-1980. A Survey of Their Biochemical and Physiological Roles in Higher Plants University of Geneva Geneva, 1982. 

Some haem proteins undergo a peroxidase cycle like that in Fig. 2, but very slowly, e.g. myoglobin converting to ferryl myoglobin. In this case the reaction is presumed not to have a physiological role. Indeed, it can have deleterious consequences (see section 5). 

The true physiological role of cytochrome c peroxidase in yeast is yet to be established. It may serve as a part of the systems which prevent intracellular accumulation of harmful hydrogen peroxide. It would be of interest to know if cytochrome c peroxidase is synthesized concurrently with or in competition with the production of other peroxide-decomposing systems such as catalase. Although cytochrome c peroxidase is present in mitochondria of aerobically grown yeast in a concentration comparable to that of cytochrome oxidase (19) and possesses an extremely high molecular activity (fcj = 10 sec ) toward yeast ferrocytochrome c (17), it has not been unequivocally shown that ferrocytochrome c is a true substrate of this enzyme. 

Ishikawa, T., Yoshimura, K., Sakai, K., Tamoi, M., Takeda, T., and Shigeoka, S., 1998, Molecular characterisation and physiological role of a glyoxysome-bound ascorbate peroxidase from spinach. Plant Cell Physiol. 39 23n34. 

Prostaglandin H synthase is the first enzyme involved in the arachidonic acid cascade . The prostaglandins can cause both relaxation and tension in smooth muscle and so have vital physiological roles. Prostaglandin H synthase acts as both a peroxidase and an oxygenase its so-called cyclooxygenase activity involves addition of two equivalents of oxygen to a free radical derived from arachidonic acid to form an endoperoxide... 

Peroxidases are important enzymes that are present in leukocytes and some tissues that have important physiological roles in the innate immune system and have been implicated in a broad spectrum of tissue pathologies. Three peroxidases that... 

On the other hand, accurate data on a theoretically sound basis are a prerequisite for the study (rf the reaction mechanism, the chemistry, and the physiological role of catalases and peroxidases. This kind of research employs, as a rule, purified enzyme preparations in transparent solutions, although Chance (99) has worked out rapid and sensitive spectrophoto-metric methods for the detailed kinetic study of hemoproteins in turbid cell su nsions. 

Brownleader M.D. Hopkins J. Mobasheri A. et al. (2002) Role of extension peroxidases in tomato Lycopersicon esculentum MiU.) seedling growth // Planta V. 210. P. 668-676. Burhanova G.F. Yarullina L. G. Maksimov I. V. (2007) Effect of chitooligosaccharides on wheat defence responses to infection by Bipolaris sorokiniana / / Russ. J. of plant physiology. V. 54. P. 104 -110. 

A Chapter of this volume is devoted to these techniques, which are merely illustrated in this section by one particular example. The electron transfer system that is the most intensively submitted to genetic manipulations is certainly the physiological complex between yeast cytochrome c and peroxide-oxidized cytochrome c peroxidase, which presents many advantages [143], Among the modifications performed on cytochrome c peroxidase, one may mention the substitution of Trp 191 which interacts directly with His 175 of the heme [144], and of His 181 [145] which was proposed as a bridging unit in a superexchange path involving Phe 87 of cytochrome c [136,146]. On the cytochrome c side, Phe 87 las been substituted [147], as well as other residues expected to play an important role in the stabilization of the noncovalent complex [143]. 

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