TRNA(His) guanylyltransferase

tRNA(His) guanylyltransferase (EC 2.7.7.79, histidine tRNA guanylyltransferase, Thg1p, Thg1) is an enzyme with systematic name p-tRNA(His):GTP guanylyltransferase (ATP-hydrolysing).^{[1][2][3][4][5][6]} This enzyme catalyses the following chemical reaction

p-tRNA(His) + ATP + GTP ${\displaystyle \rightleftharpoons }$ pppGp-tRNA(His) + AMP + diphosphate (overall reaction)

(1a) p-tRNA(His) + ATP ${\displaystyle \rightleftharpoons }$ App-tRNA(His) + diphosphate

(1b) App-tRNA(His) + GTP ${\displaystyle \rightleftharpoons }$ pppGp-tRNA(His) + AMP

tRNA(His) guanylyltransferase
Identifiers
EC no.	2.7.7.79
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Search PMC articles PubMed articles NCBI proteins

The enzyme requires a divalent cation for activity.

Thg1 enzymes are the only nucleic acid polymerases known to be capable of catalyzing nucleotide addition in the 3′–5′ direction.^[7]