Purification and characterization of ADP-ribosyl cyclase from Euglena gracilis

ADP-ribosyl cyclase, which catalyzes the conversion from NAD(+) to cyclic a denosine diphosphoribose (cADPR), is proposed to participate in cell cycle regulation in Euglena gracilis, This enzyme, which was found as a membrane- bound protein, was purified almost the homogeneity after solubilization wit h deoxycholate, and found to be a monomeric protein with a molecular mass o f 40 kDa. Its K-m value for NAD(+) was estimated to be 0.4 mM, and cADPR, a product of the enzyme, inhibited the enzyme competitively with respect to NAD(+) whereas another product, nicotinamide, showed noncompetitive (mixed- type) inhibition. In contrast to mammalian CD38 and BST-1, Euglena ADP-ribo syl cyclase lacked cADPR hydrolase activity.