TRANSFER-RNA SPLICING IN YEAST AND WHEAT-GERM - A CYCLIC PHOSPHODIESTERASE IMPLICATED IN THE METABOLISM OF ADP-RIBOSE 1'',2''-CYCLIC PHOSPHATE

Adenosine diphosphate (ADP)-ribose 1'',2'' cyclic phosphate (Appr>p) i s produced as a result of transfer RNA (tRNA) splicing in the yeast Sa ccharomyces cerevisiae and probably in other eukaryotes. Endonucleolyt ic cleavage and ligation result in a mature length tRNA with a 2'-phos phate at the splice junction. This 2'-phosphate is transferred to NAD to produce Appr>p. Metabolism of Appr>p requires hydrolysis of the 1'' ,2''-cyclic phosphate linkage. We show here that yeast has a unique cy clic phosphodiesterase that can hydrolyze Appr>p, ribose 1,2-cyclic ph osphate, and ribose 1,3-cyclic phosphate to the crresponding ribose 1- phosphate derivatives. The cyclic phosphodiesterase is highly specific for Appr>p; there is 20-fold less activity on ribose 1,3-cyclic phosp hate and no detectable activity on nucleoside 2',3'-cyclic phosphates. A similar cyclic phosphodiesterase is present in wheat germ. The whea t perm cyclic phosphodiesterase activity co-chromatographs with a 2',3 '-cyclic nucleotide 3'-phosphodiesterase that was previously identifie d and purified. The purified wheat germ enzyme has a distinct preferen ce for Appr>p and ribose cyclic phosphate compared to guanosine 2',3'- cyclic phosphate and shares other biochemical characteristics with the yeast enzyme.