Characterization of two contiguous-dimer taurocyamine kinases from the parasitic trematodes Schistosoma japonicum and Clonorchis sinensis
Phosphagen kinases (PKs) are a family of enzymes that catalyze the reversible transfer of a high-energy gamma phosphate from ATP to a guanidino acceptor molecule. Recently PKs have been proposed as a potential chemotherapeutic drug target in certain pathogens or pests. The work presented here sought to determine the suitability of two novel contiguous-dimer taurocyamine kinases (TK) from the human parasitic flukes Schistosoma japonicum (SjTK) and Clonorchis sinensis as potential anti-parasitic drug targets. 31P-NMR analysis supports the classification of these enzymes as TKs and global kinetic analysis of SjTK reacting with taurocyamine and MgATP was performed (Vmax 1.7 Â± 0.095 uM/sec, Km taurocyamine 0.33 Â± 0.037 mM, Km MgATP 0.63 Â± 0.066 mM, Ka' 0.053 Â± 0.019 mM, and kcat of 72 Â± 4.0 s-1). Further kinetic investigation revealed that SjTK exhibits the unusual characteristic of substrate inhibition with both ATP and taurocyamine; however, Ki values suggest only taurocyamine inhibition is physiologically relevant. Quaternary structure analysis shows SjTK and CsTK are dimeric but lack the highly conserved homodimer-binding motif in both domains. This suggests that the interactions leading to dimerization in these TKs may be different than in other dimeric PKs. The results of this study support SjTK and CsTK as potential drug targets for parasitic disease management and warrants further investigation. This project was made possible by the support of USDA grant 2011-68004-30104 and the Henry J. Copeland Fund for Independent Study.
© Copyright 2013 Brittany Begres