The past year has witnessed a major advance in the study of polyketide and nonribosomal peptide biosynthesis with the identification of the phosphopantetheinyl transferase enzyme family, enzymes required to produce active, post-translationally modified polyketide and peptide synthases. Phosphopantetheinyl transferases required for fatty acid, peptide and siderophore biosynthesis have been characterized and a consensus sequence noted in order to facilitate future identification of additional proteins catalyzing phosphopantetheinyl transfer.