title: Reaction mechanism for automodification of poly(ADP-ribose) synthetase.
abstract: The reaction mechanism of automodification of poly (ADP-ribose) synthetase was studied. The synthetase, bound to nicked DNA-cellulose in a small column, was pulse-labelled with [3H]NAD in the presence of Mg2+, and then chased with [14C]NAD under the same conditions after complete washing of [3H]NAD. The poly(ADP-ribose), synthesized on the synthetase molecule, was digested with snake venom phosphodiesterase and analyzed. The [3H]-labeled product (35% of the total product) was identified as isoADP-ribose but [3H]-labelled AMP was not detected. The average chain length was 16.0 and the terminal AMP was detected as [14C]-labelled AMP. These results indicate that the initially attached ADP-ribose unit at an automodification site was successively elongated by the addition of a new ADP-ribose unit to the terminal AMP moiety.
mesh_terms: D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*
chemical_list: D009243:NAD; D000246:Adenosine Diphosphate Ribose; D011065:Poly(ADP-ribose) Polymerases; D008274:Magnesium