Dipeptidyl-peptidase IV secreted by Aspergillus fumigatus, a fungus pathogenic to humans

Abstract

A dipeptidyl-peptidase IV was purified from the culture medium of the human-pathogenic fungus Aspergillus fumigatus. The enzyme has an apparent molecular mass of 95 kDa and contained approximately 10 kDa of N-linked carbohydrate. This glycoprotein is antigenic and has all characteristics of the class IV dipeptidyl-peptidases: removal of Xaa-Pro and to a lesser extent Xaa-Ala dipeptides from the N termini of peptides, including bioactive peptides such as neuropeptide Y, [des-Arg1] bradykinin, and glucagon-like peptide 1, activity at neutral pH, and presence in the amino acid sequence of the Gly-X-Ser-X-Gly consensus motif of the serine-hydrolases and the putative catalytic triad (Ser613, Asp690, His725) of the dipeptidyl-peptidases. Moreover, the last 200 amino acids displayed 60 to 65% similarity with the other dipeptidyl-peptidases IV from rat, mouse, human, and yeast. However, unlike the other dipeptidyl-peptidases, the dipeptidyl-peptidase IV of A. fumigatus is a secreted enzyme with a cleavable signal peptide. Expression of a recombinant dipeptidyl-peptidase IV of A. fumigatus has been attained in the yeast Pichia pastoris.