Figure 1. Synthesis and degradation of cADPR by T. gondii.

(A) Activity of ADP-ribosyl cyclase from T. gondii homogenates incubated with 1 mM NAD as described in the Experimental section. (B) Hydrolysis of cADPR. T. gondii homogenates were incubated with 10 μM cADPR and the remaining cADPR was determined as described in the Experimental section. (C) Extracts from T. gondii were assayed for cyclase activity using 0.2 mM NGD as a substrate, and effects of several inhibitors and stimulators of the cyclase activity and the optimal pH were tested. (D) Extracts were incubated with cyclase stimulators or inhibitors 1 min before the addition of the cyclase substrate NGD. The incubations were performed with: none (CTL), 1 mM nicotinamide (NM), 1 mM dithiothreitol (DTT), 1 mM ZnCl₂ and 1 mM ZnCl₂+1 mM EDTA. *P<0.05 indicates significant difference from control (Student's t test).