Cyclolization of D-lysergic acid alkaloid peptides.

The tripeptide chains of the ergopeptines, a class of pharmacologically important D-lysergic acid alkaloid peptides, are arranged in a unique bicyclic cyclol based on an amino-terminal α-hydroxyamino acid and a terminal orthostructure. D-lysergyl-tripeptides are assembled by the nonribosomal peptide synthetases LPS1 and LPS2 of the ergot fungus Claviceps purpurea and released as N-(D-lysergyl-aminoacyl)-lactams. We show total enzymatic synthesis of ergopeptines catalyzed by a Fe²⁺/2-ketoglutarate-dependent dioxygenase (EasH) in conjunction with LPS1/LPS2. Analysis of the reaction indicated that EasH introduces a hydroxyl group into N-(D-lysergyl-aminoacyl)-lactam at α-C of the aminoacyl residue followed by spontaneous condensation with the terminal lactam carbonyl group. Sequence analysis revealed that EasH belongs to the wide and diverse family of the phytanoyl coenzyme A hydroxylases. We provide a high-resolution crystal structure of EasH that is most similar to that of phytanoyl coenzyme A hydroxylase, PhyH, from human.