The specific, submicromolar- K m ADP-ribose pyrophosphatase purified from human placenta is enzymically indistinguishable from recombinant NUDT9 protein, including a selectivity for Mn 2+ as activating cation and increase in K m for ADP-ribose, both elicited by H 2O 2

• Published in: Biochimica et biophysica acta. General subjects Vol. 1760; no. 10; pp. 1545 - 1551
• Main Authors: Carloto, António, Costas, María Jesús, Cameselle, José Carlos, McLennan, Alexander G., Ribeiro, João Meireles
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2006
• Subjects: Adenosine diphosphate ribose; Adenosine diphosphate ribose pyrophosphatase; Hydrogen peroxide; Nudix hydrolase; Oxidative stress; GSSG; Oxidative stress; Hydrogen peroxide; DTT; Nudix hydrolase; FPC; Adenosine diphosphate ribose pyrophosphatase; IRD; NDP; NAPQI; TRPM; Adenosine diphosphate ribose
• ISSN: 0304-4165; 1872-8006
• DOI: 10.1016/j.bbagen.2006.06.003

Free ADP-ribose is a putative second messenger and also a potentially toxic compound due to its non-enzymic reactivity towards protein side chains. ADP-ribose hydrolysis is catalysed by NDP-sugar/alcohol pyrophosphatases of differing specificity, including a highly specific, low- K m ADP-ribose pyrophosphatase. In humans, a submicromolar- K m ADP-ribose pyrophosphatase has been purified from placenta, while recombinant NUDT9 has been described as a similarly specific enzyme with a nudix motif, but with a 10 2–10 3 higher K m. Here, a comparative study of both proteins is presented showing that they are in fact enzymically indistinguishable; crucially, they both have submicromolar K m for ADP-ribose. This study firmly supports the view that the ADP-ribose pyrophosphatase present in human tissues is a product of the NUDT9 gene. In addition, this study reveals previously unknown properties of both enzyme forms. They display the same, differential properties in the presence of Mg 2+ or Mn 2+ as activating cations with respect to substrate specificity, ADP-ribose saturation kinetics, and inhibition by fluoride. Treatment with H 2O 2 alters the Mg 2+/Mn 2+ responses and increases the K m values for ADP-ribose, changes that are reversed by DTT. The results are discussed in relation to the proposed roles for ADP-ribose in oxidative/nitrosative stress and for ADP-ribose pyrophosphatase as a protective enzyme whose function is to limit the intracellular accumulation of ADP-ribose.