Studies on Poly (Adenosine Diphosphate Ribose): V. MECHANISM OF HYDROLYSIS OF POLY(ADENOSINE DIPHOSPHATE RIBOSE) BY SNAKE VENOM PHOSPHODIESTERASE

Abstract

Abstract The hydrolytic action of snake venom phosphodiesterase on poly(adenosine diphosphate ribose) was investigated in comparison with that of rat liver phosphodiesterase. The purified polymer, labeled with 32P or 14C, was partially hydrolyzed with snake venom phosphodiesterase and passed through a Sephadex G-50 column. The resulting elution profiles showed the existence of degradation products with various chain lengths, which were eluted successively after the void volume. A paper chromatogram of partially hydrolyzed 14C-labeled polymer indicated the existence of a different oligomer of 2'-(5''-phosphoribosyl)adenosine 5'-phosphate, from that found after hydrolysis with rat liver phosphodiesterase. Phosphate esters in the acid-soluble products of partial digestion of 32P-labeled polymer by snake venom phosphodiesterase were not completely susceptible to alkaline phosphomonoesterase from Escherichia coli. To confirm the endonucleolytic cleavage by snake venom phosphodiesterase, the structure of the oligomer obtained by rechromatography was examined. The oligomer was incubated with alkaline phosphomonoesterase and then this was removed and it was completely hydrolyzed by snake venom phosphodiesterase. 2'-(5''-Phosphoribosyl)adenosine, 2'-(5''-phosphoribosyl)-adenosine 5'-phosphate, and 2'-ribosyladenosine 5'-phosphate were found in the hydrolysate. From these results it is concluded that snake venom phosphodiesterase digests the polymer endonucleolytically. This is in contrast to rat liver phosphodiesterase which digests it exonucleolytically.