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Pakistan Journal of Biological Sciences

Year: 2001 | Volume: 4 | Issue: 3 | Page No.: 289-292
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Authors

Golam Sadik

Kazuya Takeda

Hiroyuki Kaji

Masato Taoka

Tomotaka Shinoda

Keywords

Research Article

In vitro Generation of Amyloid βA4 Peptide from Amyloid Protein Precursor Through Nonspecific Proteolysis

Golam Sadik, Kazuya Takeda, Hiroyuki Kaji, Masato Taoka and Tomotaka Shinoda
Amyloid βA4 peptide, the principal constituents of the senile plaques in Alzheimer`s disease (AD) originates from proteolysis of a larger protein precursor (APP). Several lines of evidence suggest that this peptide may be generated from aggregated precursor through nonspecific proteolysis. In this work, we used a sensitive in vitro method of detection to investigate the role of nonspecific proteases in the processing of a 100-amino acid C-terminal fragment (C100) inclusive of βA4 and cytoplasmic domain of APP. We demonstrate first that C100 forms high molecular weight aggregates in vitro as determined by size exclusion chromatography. Digestion of aggregated C100 with the nonspecific enzyme, proteinase K resulted in cleavage at the amyloidogenic -secretase sites. This occurred at Ala 42-Val 43 generating βA4 12-42 & βA4 16-42 amyloid peptides. The enzyme cleaved most of the peptide bonds of the cytoplasmic domain and the upstream of βA4 domain of the substrate. The result suggests that both the N- and C-terminus βA4 can be generated by nonspecific proteases, acting on a aggregated substrate and support the notion that the βA4 can be formed in organelles containing proteases capable of cleaving most peptide bonds.
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