Ascaris lumbricoides β carbonic anhydrase: A potential target enzyme for treatment of ascariasis

Background: a parasitic roundworm,ascaris lumbricoides,is the causative agent of ascariasis,with approximately 760 million cases around the world. helminthic infections occur with a high prevalence mostly in tropical and developing xcountries. therefore,design of affordable broad-spectrum anti-helminthic agents against a variety of pathogens,including not only a. lumbricoides but also hookworms and whipworms,is desirable. beta carbonic anhydrases (β-cas) are considered promising targets of novel anthelminthics because these enzymes are present in various parasites,while completely absent in vertebrates. methods: in this study,we identified an a. lumbricoides β-ca (aibca) protein from protein sequence data using bioinformatics tools. we used computational biology resources and methods (including interpro,cath/gene3d,kegg,and metacyc) to analyze albca and define potential roles of this enzyme in biological pathways. the albca gene was cloned into pfastbac1,and recombinant aibca was produced in sf-9 insect cells. kinetics of albca were analyzed by a stopped-flow method. results: multiple sequence alignment revealed that aibca contains the two sequence motifs,cxdxr and hxxc,typical for β-cas. recombinant aibca showed significant ca catalytic activity with kcat of 6.0 × 105 s-1 and kcat/km of 4.3 × 107 m-1 s-1. the classical ca inhibitor,acetazolamide,showed an inhibition constant of 84.1 nm. computational modeling suggests that the molecular architecture of aibca is highly similar to several other known β-ca structures. functional predictions suggest that aibca might play a role in bicarbonate-mediated metabolic pathways,such as gluconeogenesis and removal of metabolically produced cyanate. conclusions: these results open new avenues to further investigate the precise functions of β-cas in parasites and suggest that novel β-ca specific inhibitors should be developed and tested against helminthic diseases. © 2015 zolfaghari emameh et al.