The synthesis of various benzamides is described. These, and various other compounds, were screened for their ability to inhibit the nuclear enzyme, poly(ADP-ribose) synthetase. Benzamide and various analogues substituted in the 3-position were more potent inhibitors than any described previously. 3-Aminobenzamide and 3-methoxybenzamide inhibited the enzyme competitively with respect to its substrate, NAD. 3-Aminobenzamide was shown to inhibit ADP-ribosylation in permeabilized L1210 cells but no other enzymes involved in NAD metabolism. It was demonstrated that 3-aminobenzamide entered L1210 cells. No effect on cell proliferation was observed at concentrations up to 5mM. At concentrations above this, a decrease in the rate of division was seen. Radioactive thymidine and uridine incorporation into acid-insoluble material was unaffected by 2mM 3-aminobenzamide. [3H]-Adenosine incorporation was inhibited and [3H]-leucine incorporation was transiently stimulated. NAD levels in L1210 cells increased upon 3-aminobenzamide treatment compared to controls. The suitability of 3-aminobenzamide as a probe in vivo and the approach of using inhibitors of poly(ADP-ribose) synthetase in vivo are discussed. Regulatory functions previously ascribed to ADP-ribosylation of nuclear proteins are discussed in view of the present findings.
|Date of Award||1981|