IUBMB Enzyme Nomenclature


Accepted name: CCA tRNA nucleotidyltransferase

Reaction: (1) a tRNA precursor + 2 CTP + ATP = a tRNA with a 3' CCA end + 3 diphosphate (overall reaction)
(1a) a tRNA precursor + CTP = a tRNA with a 3' cytidine end + diphosphate
(1b) a tRNA with a 3' cytidine + CTP = a tRNA with a 3' CC end + diphosphate
(1c) a tRNA with a 3' CC end + ATP = a tRNA with a 3' CCA end + diphosphate

Other name(s): CCA-adding enzyme, tRNA adenylyltransferase, tRNA cytidylyltransferase, tRNA CCA-pyrophosphorylase; tRNA-nucleotidyltransferase; transfer-RNA nucleotidyltransferase; transfer ribonucleic acid nucleotidyl transferase; CTP(ATP):tRNA nucleotidyltransferase; transfer ribonucleate adenylyltransferase; transfer ribonucleate adenyltransferase; transfer RNA adenylyltransferase; transfer ribonucleate nucleotidyltransferase; ATP (CTP):tRNA nucleotidyltransferase; ribonucleic cytidylic cytidylic adenylic pyrophosphorylase; transfer ribonucleic adenylyl (cytidylyl) transferase; transfer ribonucleic-terminal trinucleotide nucleotidyltransferase; transfer ribonucleate cytidylyltransferase; ribonucleic cytidylyltransferase; -C-C-A pyrophosphorylase; tRNA cytidylyltransferase; ATP(CTP)-tRNA nucleotidyltransferase; tRNA adenylyl(cytidylyl)transferase; CTP:tRNA cytidylyltransferase

Systematic name: CTP,CTP,ATP:tRNA cytidylyl,cytidylyl,adenylyltransferase

Comments: The acylation of all tRNAs with an amino acid occurs at the terminal ribose of a 3' CCA sequence. The CCA sequence is added to the tRNA precursor by stepwise nucleotide addition performed by a single enzyme that is ubiquitous in all living organisms. Although the enzyme has the option of releasing the product after each addition, it prefers to stay bound to the product and proceed with the next addition [5].

Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Schofield, P. and Williams, K.R. Purification and some properties of Escherichia coli tRNA nucleotidyltransferase. J. Biol. Chem. 252 (1977) 5584-5588. [PMID: 328503]

2. Shi, P.Y., Maizels, N. and Weiner, A.M. CCA addition by tRNA nucleotidyltransferase: polymerization without translocation. EMBO J. 17 (1998) 3197-3206. [PMID: 9606201]

3. Augustin, M.A., Reichert, A.S., Betat, H., Huber, R., Morl, M. and Steegborn, C. Crystal structure of the human CCA-adding enzyme: insights into template-independent polymerization. J. Mol. Biol. 328 (2003) 985-994. [PMID: 12729736]

4. Yakunin, A.F., Proudfoot, M., Kuznetsova, E., Savchenko, A., Brown, G., Arrowsmith, C.H. and Edwards, A.M. The HD domain of the Escherichia coli tRNA nucleotidyltransferase has 2',3'-cyclic phosphodiesterase, 2'-nucleotidase, and phosphatase activities. J. Biol. Chem. 279 (2004) 36819-36827. [PMID: 15210699]

5. Hou, Y.M. CCA addition to tRNA: implications for tRNA quality control. IUBMB Life 62 (2010) 251-260. [PMID: 20101632]

[EC created 1965 as EC and EC, both transferred 2010 to EC]

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