Manganese Dependent ADP Ribose/CDP Alcohol Diphosphatase (ADPRM)

ADPRibase-Mn (Mn2+-dependent ADP-ribose/CDP-alcohol pyrophosphatase) was earlier isolated from rat liver supernatants after separation from ADPRibase-I and ADPRibase-II (Mg2+-activated ADP-ribose pyrophosphatases devoid of CDP-alcohol pyrophosphatase activity). The last mentioned are putative Nudix hydrolases, whereas the molecular identity of ADPRibase-Mn is unknown. MALDI (matrix-assisted laser-desorption ionization) MS data from rat ADPRibase-Mn pointed to a hypothetical protein that was cloned and expressed and showed the expected specificity. ADP-ribose was successfully docked to a model of rat ADPRibase-Mn, revealing its putative active centre. Furthermore, the influence of ADPRibase-Mn on the CDP-choline or CDP-ethanolamine pathways of phospholipid biosynthesis cannot be discounted.