Also known as FBID_MYCSJ, fbiD. Guanylyltransferase that catalyzes the activation of phosphoenolpyruvate (PEP) as enolpyruvoyl-2-diphospho-5'-guanosine, via the condensation of PEP with GTP. It is involved in the biosynthesis of coenzyme F420, a hydride carrier cofactor.