Mechanisms of poly(ADP-ribose) polymerase catalysis; mono-ADP-ribosylation of poly(ADP-ribose) polymerase at nanomolar concentrations of NAD.
Calf thymus and rat liver poly(ADP-ribose) polymerase enzymes, and the polymerase present in extracts of rat liver nuclei synthesize unstable mono-ADP-ribose protein adducts at 100 nM or lower NAD concentrations. The isolated enzyme-mono-ADP-ribose adduct hydrolyses to ADP-ribose and enzyme protein at pH values slightly above 7.0 indicating a continuous release of ADP-ribose from NAD through this enzyme-bound intermediate under physiological conditions. NH2OH at pH 7.0 hydrolyses the mono-ADP-ribose enzyme adduct. Desamino NAD and some other homologs at nanomolar concentrations act as 'forward' activators of the initiating mono-ADP-ribosylation reaction. These NAD analogs at micromolar concentrations do not affect polymer formation that takes place at micromolar NAD concentrations. Benzamides at nanomolar concentrations also activate mono-ADP-ribosylation of the enzyme, but at higher concentrations inhibit elongation at micromolar NAD as substrate. In nuclei, the enzyme molecule extensively auto-ADP-ribosylates itself, whereas histones are trans-ADP-ribosylated to a much lower extent. The unstable mono-ADP-ribose enzyme adduct represents an initiator intermediate in poly ADP-ribosylation.
D036002:ADP Ribose Transferases; D000246:Adenosine Diphosphate Ribose / Q000378:metabolism*; D000818:Animals; D002417:Cattle; D019811:Hydroxylamine; D006898:Hydroxylamines / Q000494:pharmacology; D007700:Kinetics; D009243:NAD / Q000378:metabolism*; D009536:Niacinamide / Q000494:pharmacology; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*
D006898:Hydroxylamines; D009702:Nucleoside Diphosphate Sugars; D009243:NAD; D000246:Adenosine Diphosphate Ribose; D009536:Niacinamide; D019811:Hydroxylamine; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases