Concerted action of dipeptidyl peptidase IV and glutaminyl cyclase results in formation of pyroglutamate-modified amyloid peptides in vitro

Compelling evidence suggests a crucial role of amyloid beta peptides (A beta(1-40/42)) in the etiology of Alzheimer's disease (AD). The N-terminal truncation of A beta(1-40/42) and their modification, e.g. by glutaminyl cyclase (QC), is expected to enhance the amyloid toxicity. In this work, the MALDI-TOF mass spectrometry application proved N-terminal cleavage of A beta(1-40/42) by purified dipeptidyl peptidase IV (DPPIV) in vitro observed earlier. The subsequent transformation of resulted A beta(3-40/42) to pE-A beta(3-40/42) in QC catalyzed glutamate cyclization was manifested. Hence, consecutive conversion of A beta(1-40/42) by DPPIV and QC can be assumed as a potential mechanism of formation of non-degrading pyroglutamated pE-A beta(3-40/42), which might accumulate and contribute to AD progression. The in vitro acceleration of A beta(1-40) aggregation in the simultaneous presence of DPPIV and QC was shown also. (C) 2017 Published by Elsevier Ltd.