Requires Mn2+, which cannot be replaced by Mg2+, for activity. ADP-D-ribose, CDP-choline, CDP-ethanolamine and ADP are substrates for this enzyme but ADP-D-glucose, UDP-D-glucose, CDP-D-glucose, CDP, CMP and AMP are not hydrolysed [2]. In rat, the enzyme is found predominantly in thymus and spleen.