Spectroscopic and calorimetric assays reveal dependence on dCTP and two metals (Zn2 + + Mg2 +) for enzymatic activity of Schistosoma mansoni deoxycytidylate (dCMP) deaminase

- In solution analysis indicates that S. mansoni dCMP deaminase is a hexamer in solution.
- Kinetic and thermodynamic parameters of the dCMP deaminase catalytic reaction of dCMP with dCTP as a cofactor and dTTP as an inhibitor were determined by isothermal titration calorimetry.
- Mg2 +/Zn2 + and dCTP are essential cofactors for the deaminase activity of the enzyme.

The parasite Schistosoma mansoni possess all pathways for pyrimidine biosynthesis, whereby deaminases play an essential role in the thymidylate cycle, a crucial step to controlling the ratio between cytidine and uridine nucleotides. In this study, we heterologously expressed and purified the deoxycytidylate (dCMP) deaminase from S. mansoni to obtain structural, biochemical and kinetic information. Small-angle X-ray scattering of this enzyme showed that it is organized as a hexamer in solution. Isothermal titration calorimetry was used to determine the kinetic constants for dCMP-dUMP conversion and the role of dCTP and dTTP in enzymatic regulation. We evaluated the metals involved in activating the enzyme and show for the first time the dependence of correct folding on the interaction of two metals. This study provides information that may be useful for understanding the regulatory mechanisms involved in the metabolic pathways of S. mansoni. Thus, improving our understanding of the function of these essential pathways for parasite metabolism and showing for the first time the hitherto unknown deaminase function in this parasite.