Degradation of APP

Figure 12. Effect of DTBP on the thermal oxidative degradation of APP in...

Table II. Effects of Model Compounds of Oxidation Products on the Thermal Oxidative Degradation of APP in the Absence and Presence of Cu Stearate...

The thermal and thermo-oxidative degradations of APP have been reported (Hornsby et al. 1996 Camino et al. 1984 Zhang et al. 1993) they are similar and consist of two steps. The degradation begins around 300 °C with the elimination of NH3, leading to the formation of a highly cross-linked polyphosphoric acid, whereas the second step above 550 °C corresponds to polyphosphoric acid evaporation and/or dehydration to P4O10 which sublimes. 

Controlled degradation of APP in air at 150-300°C in the presence of d -tert-hvXy peroxyisopropylben-zene increases the polymer functionality and reduces its isotactic content and branching. The product can be used in the processing of polyolefins and in adhesive... 

Horrocks et al. have studied the FR features of a series metal ions combined with APP [62]. It has been demonstrated that certain metal ions, particularly Mn and Zn , anticipate the thermal degradation of APP as a consequence, the FR, applied as a back-coating to cotton fabrics, activates at lower temperatures, hence enhancing the FR efficiency, as assessed by LOI tests. Similar results were obtained by Tian and co-workers [51]. 

The enzymes that are involved in the processing of APP into amyloid peptides are known as secretases. Beta-secretase is an enzyme that catalyzes the initial proteolytic event leading to the production of Abeta amyloid peptides. If APP is cleaved by beta-secretase it can then be further cleaved by gamma-secretase. Abeta peptides are either secreted or intracellularly released. They have varying lengths and represent intermediate degradation products of its precursor (i.e., (3-secretase cleaved APP). Especially the 42 amino acid peptide (A 342) aggregates to form insoluble amyloid plaques. 

Proteasome inhibition by lactacystin and Bz-LLL-COCHO (benzol-Leu-Leu-Leu-glyoxal) causes a significant increase of ABP and cell death by altering APP processing at the y-secretase site (406). Resveratrol does not inhibit ABP production because it has no effect on 3-, or y-secretases, but promotes instead intracellular degradation of ABP via a mechanism that involves the proteasome. The resveratrol-induced decrease of ABP can be effectively prevented by several selective proteasome inhibitors and by small interfering RNA-directed silencing on the proteasome subunit P5 (407). 

Steiert, J.G., J.J. Pignatello, and R.L. Crawford. 1987. Degradation of chlorinated phenols by a pentachlo-rophenol-degrading bacterium. App/. Environ. Microbiol. 53 907-910. 

Wang, Z., Han, E., and Ke, W. 2006. Effect of acrylic polymer and nanocomposite with nano-Si02 on thermal degradation and fire resistance of APP-DPER-MEL coating. Polymer Degradation and Stability 91(9) 1937—1947. 

Orth A. B., Roye D. J., and Tien D. M. (1993) Ubiquity of lignin degrading peroxidases among various wood degrading fungi. App/. Environ. Microbiol. 59, 4017-4023. 

Edwards E. A., Wills L. E., Reinhard M., and Grbic-Galic D. (1992) Anaerobic degradation of toluene and xylene by aquifer microorganisms under sulfate-reducing conditions. App Environ. Microbiol. 58(3), 794-800. 

In addition, a study by d Abramo reported that the activation of this nuclear receptor was able to inhibit the expression of APP. They demonstrated that overexpression of PPARy in cultured cells decreased kp secretion by promoting APP degradation. They demonstrated that PPARy activation resulted in increased ubiquitination of APP, leading to its subsequent degradation [18]. 

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