DIPEPTIDYL-PEPTIDASE-IV SECRETED BY ASPERGILLUS-FUMIGATUS, A FUNGUS PATHOGENIC TO HUMANS

A dipeptidyl-peptidase IV was purified from the culture medium of the human-pathogenic fungus Aspergillas fumigatus. The enzyme has an appar ent molecular mass of 95 kDa and contained approximately 10 kDa of N-l inked carbohydrate, This glycoprotein is antigenic and has all charact eristics 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-Arg(1)] bra dykinin, and glucagon-like peptide 1, activity at neutral pH, and pres ence in the amino acid sequence of the Gly-X-Ser-X-Gly consensus motif of the serine-hydrolases and the putative catalytic triad (Ser(613), Asp(690), His(725)) of the dipeptidyl-peptidases. Moreover, the last 2 00 amino acids displayed 60 to 65% similarity with the other dipeptidy l-peptidases TV from rat, mouse, human, and yeast, However, unlike the other dipeptidyl-peptidases, the dipeptidyl-peptidase IV of A, fumiga tus is a secreted enzyme with a cleavable signal peptide, Expression o f a recombinant dipeptidylpeptidase TV of A, fumigatus has been attain ed in the yeast Pichia pastoris.