Involved in the biosynthesis of saframycin A (SFM-A), a potent antitumor antibiotic that belongs to the tetrahydroisoquinoline family (PubMed:17981978). Specifically adenylates glycine and loads it onto its peptidyl carrier domain, via a thioester linkage to the phosphopanthetheine moiety (PubMed:17981978). ATP + glycine + holo-[peptidyl-carrier protein] = AMP + diphosphate + glycyl-[peptidyl-carrier protein] Antibiotic biosynthesis. Inactivation of the gene completely abolishes the ability to produce SFM-A. Belongs to the ATP-dependent AMP-binding enzyme family.