An enzyme from Saccharomyces cerevisiae uses NAD+ to transfer the splice junction 2'-phosphate from ligated tRNA to an acceptor molecule

An enzyme from Saccharomyces cerevisiae which removes the splice junction 2'-phosphate from ligated tRNA appears to require NAD+. This two-component enzyme has been previously implicated in tRNA splicing because of its specificity for substrates bearing an internal 2'-phosphate and because of the absence of other observed proteins that can efficiently catalyze the same activity after fractionation of the extracts. We show here that component I of this enzyme is heat-stable, chromatographs as a small molecule, can be substituted efficiently by NAD+, and comigrates with NAD+ on a reversed-phase column. Dephosphorylation of ligated tRNA in the presence of component I or NAD+ is accompanied by stoichiometric transfer of the splice junction 2'-phosphate to an unidentified acceptor molecule.