Cyclization of amino acids against the peptide "backbone" is often performed, resulting in oxazolines and thiazolines; these can be further oxidized or reduced.
Nonribosomal peptides are a very diverse family of natural products with an extremely broad range of biological activities and pharmacological properties.
Each module consists of several domains with defined functions, separated by short spacer regions of about 15 amino acids.
To become functional, the 4'-phospho-pantetheine sidechain of acyl-CoA molecules has to be attached to the PCP-domain by 4'PP transferases (Priming) and the S-attached acyl group has to be removed by specialized associated thioesterases (TE-II) (Deblocking).
[10] The condensation C-domain is also believed to have substrate specificity, especially if located behind an epimerase E-domain-containing module where it functions as a 'filter' for the epimerized isomer.
Computational methods, such as SANDPUMA[11] and NRPSpredictor2,[12] have been developed to predict substrate specificity from DNA or protein sequence data.