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{{Infobox enzyme
| Name = TRNAHis guanylyltransferase
| EC_number = 2.7.7.79
| CAS_number = 
| IUBMB_EC_number = 2/7/7/79
| GO_code = 
| image = 
| width = 
| caption =
}}
'''TRNAHis guanylyltransferase''' ({{EC number|2.7.7.79}}, ''histidine tRNA guanylyltransferase'', ''Thg1p'', ''Thg1'') is an [[enzyme]] with system name ''p-tRNAHis:GTP guanylyltransferase (ATP-hydrolysing)''.<ref>{{cite journal | title = Histidine tRNA guanylyltransferase from ''Saccharomyces cerevisiae''. II. Catalytic mechanism |author = Jahn, D. and Pande, S. |journal = J. Biol. Chem. |year = 1991 |volume = 266 |pages = 22832–22836 |pmid = 1660462}}</ref><ref>{{cite journal | title = Histidine tRNA guanylyltransferase from ''Saccharomyces cerevisiae''. I. Purification and physical properties |author = Pande, S., Jahn, D. and Soll, D. |journal = J. Biol. Chem. |year = 1991 |volume = 266 |pages = 22826–22831 |pmid = 1660461}}</ref><ref>{{cite journal | title = tRNA<sup>His</sup> maturation: an essential yeast protein catalyzes addition of a guanine nucleotide to the 5&prime; end of tRNA<sup>His</sup> |author = Gu, W., Jackman, J.E., Lohan, A.J., Gray, M.W. and Phizicky, E.M. |journal = Genes Dev. |year = 2003 |volume = 17 |pages = 2889–2901 |pmid = 14633974}}</ref><ref>{{cite journal | title = Plant mitochondria use two pathways for the biogenesis of tRNA<sup>His</sup> |author = Placido, A., Sieber, F., Gobert, A., Gallerani, R., Giege, P. and Marechal-Drouard, L. |journal = Nucleic Acids Res. |year = 2010 |volume = 38 |pages = 7711–7717 |pmid = 20660484}}</ref><ref>{{cite journal | title = Identification of critical residues for G-1 addition and substrate recognition by tRNA(His) guanylyltransferase |author = Jackman, J.E. and Phizicky, E.M. |journal = Biochemistry |year = 2008 |volume = 47 |pages = 4817–4825 |pmid = 18366186}}</ref><ref>{{cite journal | title = tRNA(His) guanylyltransferase (THG1), a unique 3&prime;-5&prime; nucleotidyl transferase, shares unexpected structural homology with canonical 5&prime;-3&prime; DNA polymerases |author = Hyde, S.J., Eckenroth, B.E., Smith, B.A., Eberley, W.A., Heintz, N.H., Jackman, J.E. and Doublie, S. |journal = Proc. Natl. Acad. Sci. USA |year = 2010 |volume = 107 |pages = 20305–20310 |pmid = 21059936}}</ref> This enzyme [[catalysis|catalyses]] the following [[chemical reaction]]

: p-tRNAHis + ATP + GTP <math>\rightleftharpoons</math> pppGp-tRNAHis + AMP + [[diphosphate]] (overall reaction)
: (1a) p-tRNAHis + ATP <math>\rightleftharpoons</math> App-tRNAHis + diphosphate
: (1b) App-tRNAHis + GTP <math>\rightleftharpoons</math> pppGp-tRNAHis + AMP

The enzyme requires a divalent cation for activity.

== References ==
{{reflist}}

== External links ==
* {{MeshName|TRNAHis+guanylyltransferase}}

[[Category:EC 2.7.7]]