Adenosine-5′-O-phosphorylated and adenosine-5′-O-phosphorothioylated polyols as strong inhibitors of (symmetrical) and (asymmetrical) dinucleoside tetraphosphatases

Abstract

Dinucleoside 5′,5‴-P1,Pn-polyphosphates, and particularly the diadenosine compounds, have been implicated in extracellular purinergic signalling and in various intracellular processes, including DNA metabolism, tumour suppression and stress responses. If permitted to accumulate, they may also be toxic. One approach to understanding their function is through the various specific degradative enzymes that regulate their levels. Eight adenosine-5′-O-phosphorylated polyols (derivatives of glycerol, erythritol and pentaerythritol) and 11 adenosine-5′-O-phosphorothioylated polyols (derivatives of glycerol, erythritol, pentaerythritol, butanediol and pentanediol) have been tested as inhibitors of specific diadenosine tetraphosphate (Ap4A) hydrolases. Of these two groups of novel nucleotides, the adenosine-5′-O-phosphorothioylated polyols were generally stronger inhibitors than their adenosine-5′-O-phosphorylated counterparts. 1,4-Di(adenosine-5′-O-phosphorothio) erythritol appeared to be the strongest inhibitor of (asymmetrical) Ap4A hydrolases (EC 3.6.1.17) from both lupin and human, with Ki values of 0.15 μM and 1.5 μM respectively. Of eight adenosine-5′-O-phosphorylated polyols, 1,4-di(adenosine-5′-O-phospho) erythritol was the only compound that inhibited the lupin enzyme. Two derivatives of pentaerythritol, di(adenosine-5′-O-phosphorothio)-di(phosphorothio) pentaerythritol and tri(adenosine-5′-O-phosphorothio)-phosphorothio-pentaerythritol, proved to be the strongest inhibitors of the prokaryotic (symmetrical) Ap4A hydrolase (EC 3.6.1.41) so far reported. The estimated Ki values were 0.04 μM and 0.08 μM respectively. All of these inhibitors were competitive with respect to Ap4A. These new selectively acting Ap4A analogues should prove to be valuable tools for further studies of Ap4A function and of the enzymes involved in its metabolism.