This domain is found in many multi-domain enzymes which synthesise peptide antibiotics. This domain catalyses a condensation reaction to form peptide bonds in non- ribosomal peptide biosynthesis. It is usually found to the carboxy side of a phosphopantetheine binding domain (Pfam:PF00550). It has been shown that mutations in the HHXXXDG motif abolish activity suggesting this is part of the active site [1].

1: Peptide bond formation in nonribosomal peptide biosynthesis. Catalytic role of the condensation domain. Stachelhaus T, Mootz HD, Bergendahl V, Marahiel MA; J Biol Chem 1998;273:22773-22781. PMID:9712910