Term Name:	GTP guanylyltransferase activity
Synonyms:	GTP:GTP guanylyltransferase activity, guanosine-triphosphate guanylyltransferase activity
Definition:	Catalysis of the reaction: 2 GTP + H+ = P(1),P(4)-bis(5'-guanosyl) tetraphosphate + diphosphate + H+.
Ontology:	GO: Molecular Function [GO:0047351]    QuickGO    AmiGO