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.