Molecular and biochemical analysis of an aspartylglucosaminidase from the venom of the parasitoid wasp Asobara tabida (Hymenoptera: Braconidae).

The most abundant venom protein of the parasitoid wasp Asobara tabida was identified to be an aspartylglucosaminidase (hereafter named AtAGA). The aim of the present work is the identification of: 1) its cDNA and deduced amino acid sequences, 2) its subunits organization and 3) its activity. The cDNA of AtAGA coded for a proalphabeta precursor molecule preceded by a signal peptide of 19 amino acids. The gene products were detected specifically in the wasp venom gland (in which it could be found) under two forms: an (active) heterotetramer composed of two alpha and two beta subunits of 30 and 18 kDa respectively and a homodimer of 44 kDa precursor. The activity of AtAGA enzyme showed a limited tolerance toward variations of pH and temperatures. Since the enzyme failed to exhibit any glycopeptide N-glycosidase activity toward entire glycoproteins, its activity seemed to be restricted to the deglycosylation of free glycosylasparagines like human AGA, indicating AtAGA did not evolve a broader function in the course of evolution. The study of this enzyme may allow a better understanding of the functional evolution of venom enzymes in hymenopteran parasitoids.