The CCA-adding enzyme TRNT1 (EC 2.7.7.25) is an essential enzyme that catalyzes the addition of the CCA terminus to the 3-prime end of tRNA precursors. This reaction is a fundamental prerequisite for mature tRNAs to become aminoacylated and to participate in protein biosynthesis (Lizano et al., 2007 [PubMed 17204286]).[supplied by OMIM, Aug 2009]