In vitro synthesis of new cyclodepsipeptides of the PF1022-type: probing the alpha-D-hydroxy acid tolerance of PF1022 synthetase.

The nonribosomal peptide synthetase PF1022-synthetase (PFSYN) synthesises the cyclooctadepsipeptide PF1022 from the building blocks D-lactate, D-phenyllactate and N-methylleucine. The substrate tolerance of PFSYN for hydroxy acids was probed by in vitro screening of a set of aliphatic and aromatic alpha-D-hydroxy acids with various structural modifications in the side chain. Thus, new PF1022 derivatives for example, propargyl-D-lactyl-PF1022 and beta-thienyl-D-lactyl-PF1022 were generated. The promiscuous behaviour of PFSYN towards aliphatic and aromatic alpha-D-hydroxy acids is considerably larger than that of related enniatin synthetase (ESYN) and thus gives rise to the enzymatic generation of various new PF1022 derivatives.