MECHANISM OF INHIBITION OF POLY(ADP-RIBOSE) GLYCOHYDROLASE BY ADENOSINE-DIPHOSPHATE (HYDROXYMETHYL)PYRROLIDINEDIOL

Adenosine diphosphate (hydroxymethyl)pyrrolidine diol (ADP-HPD), a nit rogen-in-the-ring analog of ADP-ribose, was recently shown to be a pot ent and specific inhibitor of poly(ADP-ribose) glycohydrolase. Analysi s of the inhibition kinetics of the hydrolase by ADP-HPD using the met hod of Lineweaver and Burk yields a noncompetitive double-reciprocal p lot. Both the intercept (1/V) versus [inhibitor] replot and the slope (K-m/V) versus [inhibitor] replot are hyperbolic, indicating partial n oncompetitive inhibition. Inhibitor dissociation constants K-ii = 52 n M and K-is = 80 nM were determined for ADP-HPD by analysis of the inte rcept versus [inhibitor] and slope versus [inhibitor] replots. These r esults show that although ADP-HPD is extremely potent in inhibiting po ly(ADP-ribose) glycohydrolase, its effectiveness is limited by its par tial inhibition. ADP-HPD was significantly less potent as an inhibitor of the NAD glycohydrolase from Bungarus fasciatus venom. Analysis of the inhibition kinetics using the Lineweaver and Burk method indicated that ADP-HPD was a linear-competitive inhibitor of the NAD glycohydro lase with a K-i of 94 mu M. The results indicate that at low concentra tion ADP-HPD will be a selective inhibitor of poly(ADP-ribose) glycohy drolase; however, complete inactivation of the activity will be diffic ult to obtain.