<p> tRNA-splicing endonucleases (<db_xref db="EC" dbkey="3.1.27.9"/>) catalyse the endonucleolytic cleavage of pre tRNA at the 5' and 3' splice sites to release the intron and produces two half tRNA molecules bearing 5' hydroxyl and 2', 3'-cyclic phosphate termini [<cite idref="PUB00054270"/>]. The genes are homologous in Eucarya and Archea. The two yeast genes have been functionally studied [<cite idref="PUB00055529"/>] and are two subunits of a heterotetramer enzyme in yeast, the other two subunits of which have no known homologs. </p>