Toxic peptide fragment

Cleavage of APPs by protease enzymes, called secretases, produces peptide fragments called amyloid-P (AP). Ap forms dense extracellular aggregates, called amyloid plaques, that cause neuronal death. APPs can be found in the human brain without causing deleterious effects. APPs protect brain cells from injury. Normally, the enzyme a-secretase cleaves APPs so that amyloid-P peptide is not produced. Amyloid P peptide is toxic to brain cells. 

The potential that the peptide could break down due to nonspecific metabolism, resulting in products that had no therapeutic value or even be a toxic fragment ... 

Yuan, M., Namikoshi, M., Otsuki, A., and Sivonen, K. 1998. Effect of amino acid side-chain on fragmentation of cyclic peptide ions differences of electrospray ionization collision-induced decomposition mass spectra of toxic heptapeptide microcystins containing ADM Adda instead of Adda. EurMass Spectrom 4 287-298. 

In experiments on transmembrane translocation of fusion proteins it is necessary to have a reliable and convenient way of monitoring translocation of the fusion protein. Measuring the toxic effect of the fusion protein provides an indication of translocation, but is not sufficient, since it only shows that the enzymatic A-fragment has been translocated. Thus, the passenger peptide or protein could have been removed proteolytically before translocation takes place. It should also be noted that monitoring toxicity is not very accurate in assessing how much A-fragment (or fusion protein) is translocated. 

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