Tpt1 catalyses the last step of tRNA splicing in yeast. It transfers the splice junction 2'-phosphate from ligated tRNA to NAD, to produce ADP-ribose 1\-2\
The final step of tRNA splicing in Saccharomyces cerevisiae (Baker's yeast) requires 2'-phosphotransferase (Tpt1) to transfer the 2'-phosphate from ligated tRNA to NAD, producing mature tRNA and ADP ribose-1' '-2' '-cyclic phosphate. Yeast and Mus musculus (Mouse) Tpt1 protein and bacterial KptA protein can catalyze the conversion of the generated intermediate to both product and the original substrate, these enzymes likely use the same reaction mechanism. Step 1 of this reaction is strikingly similar to the ADP-ribosylation of proteins catalyzed by a number of bacterial toxins.