GTP guanylyltransferase activity
Catalysis of the reaction: 2 GTP + H+ = P(1),P(4)-bis(5'-guanosyl) tetraphosphate + diphosphate + H+.
GO:0070568
guanylyltransferase activity
is_a
GTP:GTP guanylyltransferase activity
broad
guanosine-triphosphate guanylyltransferase activity
exact