Acasp,a Gene Encoding a Cathepsin D-like Aspartic Protease from the HookwormAncylostoma caninum

Abstract

Intestinal infection with the zoonotic hookwormAncylostoma caninumcan provoke human eosinophilic enteritis. A cDNA was isolated fromA. caninum,using an oligonucleotide primer designed to hybridize to the region encoding the consensus, catalytic site residues D32TGSSNLW of aspartic proteases. This novel cDNA encoded an aspartic protease zymogen of 422 amino acids, exhibiting 47% identity to the lysosomal aspartic protease ofAedes aegypti,46% identity to the aspartic protease ofSchistosoma japonicum,and 48.5% to human cathepsin D. Its deduced structure differed from that of cathepsin D in the loop 2 “flap,” which holds the substrate at the active site, and by the presence of a COOH-terminal extension of ∼30 residues.