Coenzyme F420-0 Gamma-Glutamyl Ligase Activity

GO:0043773

Catalysis of the reactions: (1) GTP + F420-0 + L-glutamate = GDP + phosphate + F420-1, and (2) GTP + F420-1 + L-glutamate = GDP + phosphate + gamma-F420-2. This is the GTP-dependent successive addition of two L-glutamates to the L-lactyl phosphodiest.