Discovery of acylsulfenic acid-featuring natural product sulfenicin and characterization of its biosynthesis.

Life's organic molecules are built with diverse functional groups that enable various importance biological functions. As such, the discovery of unique functional groups in nature can expand our understanding of the natural world. Here we report the genome-aided discovery of sulfenicin, a polyketide-non-ribosomal peptide hybrid natural product from a marine Streptomyces bacterium bearing a unique acylsulfenic acid functionality. Through a series of heterologous biosynthesis, functional genetics and enzymatic reconstitution experiments, we show that this previously described synthetic functional group is biologically assembled by a set of enzymes from both primary and secondary metabolism, including a flavin-dependent S-hydroxylase that hydroxylates the sulfur atom of a thiocarboxylic acid. Although public databases so far include no parallel for the sulfenicin biosynthetic gene cluster, enzymes catalysing the production of acylsulfenic acid are widely distributed in bacterial genomes, implying that this labile functional group may similarly have a broad distribution among specialized metabolites.