A proposed catalytic mechanism of aspergilloglutamic peptidase from Aspergillus niger

Abstract

Aspergilloglutamic peptidase from Aspergillus niger (formerly called aspergillopepsin II) is a novel pepstatin-insensitive acid endopeptidase distinct from the well-studied aspartic peptidases, and thus is an interesting target for protein structure/function studies. Our recent X-ray crystallographic and site-directed mutagenesis studies showed that the enzyme is a glutamic peptidase in which glutamic acid-110 and glutamine-24 in the heavy chain are involved in the active site, forming a catalytic dyad. In the present study, we have investigated the pH-dependence of the enzyme activity and performed docking calculations to shed light on the catalytic mechanism of the enzyme. The results suggest a novel catalytic mechanism where glutamic acid-110 acts as a general acid in the first phase of catalysis.


(Communicated by Masanori OTSUKA, M.J.A.)