Non-ribosomal peptide synthetase, able to activate proline and AEO (2-amino-9,10-epoxi-8-oxodecanoic acid), and epimerize L-Pro. Catalyzes the production of HC-toxin: a cyclic tetrapeptide. Activates and thioesterifies L-Pro, and epimerizes it to D-Pro; also uses D-Ala as a substrate but this is epimerized from L-Ala by TOXG. Binds 4 phosphopantetheines covalently. Mycotoxin biosynthesis; HC-toxin biosynthesis. Belongs to the ATP-dependent AMP-binding enzyme family. It is uncertain whether Met-1 or Met-3 is the initiator.