(164f) Amyloid Aggregation of Enzymes Under Non-Denaturing Conditions

Aberrant associations into amyloid aggregates can occur from unfolded states of proteins and are associated with various diseases. Recent evidence demonstrates that amyloid aggregation of proteins can also occur from conformational states directly accessible from native states, without substantial unfolding. The presence of aggregation-prone regions (APRs) near the active sites of many enzymes and the conformation dynamics, required for the functional roles, contribute to the high risk of amyloid aggregation even under non-denaturing conditions. These aberrant intermolecular associations occur through exposures of APRs. While the evolutionary pressures have optimized folded states of proteins for serving biological functions without the aggregation, conditions that enzymes face in industrial settings are different from where enzymes have evolved. While amyloid aggregation of an unfolded protein has been extensively studied, little is known about amyloid aggregation of a folded protein and a strategy for prevention thereof.

In our study presented herein, a folded enzyme, Bacillus circulans xylanase (BCX), aggregates into amyloid fibrils during incubation under a non-denaturing condition. We also found that the aggregation is concomitant with the loss of enzymatic activity and can be reduced by peptides derived from other amyloid proteins. Moreover, we found that different enzymes, including those with high conformational stability, also aggregates into amyloid fibrils under non-denaturing conditions, further supporting that amyloid aggregation of enzymes under non-denaturing conditions is more common than what has been reported. Collectively, our study enhances an understanding of amyloid aggregation of enzymes under non-denaturing conditions toward advances in industrial biochemical processes.