Degraded Products Of Stem Bromelain Destabilize Aggregates Of Beta-Amyloid Peptides Involved In Alzheimer'S Disease

Deposition of fibrils originating from monomeric beta-amyloid (A beta) peptide in brain cells is responsible for progressive neuronal damages in Alzheimer's disease. Peptides from bromelain, a cysteine protease from Ananas comosus (pineapple), were generated after digestion with proteases under conditions similar to human gastrointestinal tract. These peptides not only inhibit the growth of A beta-amyloid aggregates, but also irreversibly destabilize the preformed aggregates. Gel filtration followed by mass spectrometric analysis identified a pool of peptides of <700 Da in the digest. Probable composition of the peptides interacting with A beta-peptide was predicted from homology alignment between A beta-peptide and bromelain using bioinformatics tools. Corresponding synthetic peptides can also destabilize the preformed aggregates as observed from thioflavin T assay, transmission electron microscopy and atomic force microscopy. A beta aggregates that were preincubated with the bromelain-derived peptides did not exert appreciable toxicity on human neuroblastoma cells (SH-SY5Y) cultured in vitro.