Ascaris lumbricoides beta carbonic anhydrase: a potential target enzyme for treatment of ascariasis

作者：Emameh Reza Zolfaghari^*; Kuuslahti Marianne; Vullo Daniela; Barker Harlan R; Supuran Claudiu T; Parkkila Seppo

来源：Parasites & Vectors, 2015, 8(1): 479.

DOI：10.1186/s13071-015-1098-5

• Ascaris lumbricoides
• Beta carbonic anhydrase
• Enzyme inhibition
• Sulfonamide
• Acetazolamide
• Bioinformatics
• Computational biology
• 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 (beta-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 beta-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 beta-CAs. Recombinant AIBCA showed significant CA catalytic activity with k(cat) of 6.0 x 10(5) s(-1) and k(cat)/K-M of 4.3 x 10(7) 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 beta-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 beta-CAs in parasites and suggest that novel beta-CA specific inhibitors should be developed and tested against helminthic diseases.

• 出版日期2015-9-18