Molecular and catalytic properties of an arginine kinase from the nematodeAscaris suum

Abstract

AbstractWe amplified the cDNA coding for arginine kinase (AK) from the parasitic nematodeAscaris suum, cloned it in pMAL plasmid and expressed the enzyme as a fusion protein with the maltose-binding protein. The whole cDNA was 1260 bp, encoding 400 amino acids, and the recombinant protein had a molecular mass of 45,341 Da.Ascaris suumrecombinant AK showed significant activity and strong affinity( K _{m}^{Arg} = 0.126\hairsp mM)for the substratel-arginine. It also exhibited high catalytic efficiency( k _{cat}/ K _{m}^{Arg} = 352)comparable with AKs from other organisms. Sequence analysis revealed high amino acid sequence identity betweenA. suumAK and other nematode AKs, all of which cluster in a phylogenetic tree. However, comparison of gene structures showed thatA. suumAK gene intron/exon organization is quite distinct from that of other nematode AKs. Phosphagen kinases (PKs) from certain parasites have been shown to be potential novel drug targets or tools for detection of infection. The characterization ofA. suumAK will be useful in the development of strategies for control not only ofA. suumbut also of related species infecting humans.