Each of the constituent amino acids of the tripeptide acv are activated as aminoacyl-adenylates with peptide bonds formed through the participation of amino acid thioester intermediates. 3 ATP + H2O + L-2-aminoadipate + L-cysteine + L-valine = 3 AMP + 3 diphosphate + 3 H(+) + N-[(5S)-5-amino-5-carboxypentanoyl]-L-cysteinyl-D-valine Binds 3 phosphopantetheines covalently. Antibiotic biosynthesis; penicillin G biosynthesis; penicillin G from L-alpha-aminoadipate and L-cysteine and L-valine: step 1/3. Belongs to the ATP-dependent AMP-binding enzyme family.