MRNA guanylyltransferase

In enzymology, a mRNA guanylyltransferase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are GTP and (5')ppPur-mRNA, whereas its two products are diphosphate and G(5')pppPur-mRNA.
This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is GTP:mRNA guanylyltransferase. Other names in common use include mRNA capping enzyme, messenger RNA guanylyltransferase, and Protein 2.
Structural studies.
As of late 2007, 5 structures have been solved for this class of enzymes, with PDB accession codes , , , , and .