S1 pocket of glutamate carboxypeptidase II: a new binding site for amyloid-β degradation.

Abstract We recently reported that glutamate carboxypeptidase II (GCPII) has a new physiological function degrading amyloid- β (A β ), distinct from its own hydrolysis activity in N-acetyl-L-aspartyl-L-glutamate (NAAG); however, its underlying mechanism remains undiscovered. Using site-directed mutagenesis and S1 pocket-specific chemical inhibitor (compound 2), which was developed for the present study based on in sillico computational modeling, we discovered that the A β degradation occurs through S1 pocket but not through S1′ pocket responsible for NAAG hydrolysis. Treatment with compound 2 prevented GCPII from A β degradation without any impairment in NAAG hydrolysis. Likewise, 2-PMPA (specific GCPII inhibitor developed targeting S1′ pocket) completely blocked the NAAG hydrolysis without any effect on A β degradation. Pre-incubation with NAAG and A β did not affect A β degradation and NAAG hydrolysis, respectively. These data suggest that GCPII has two distinctive binding sites for two different substrates and that Aβ degradation occurs through binding to S1 pocket of GCPII.