title: An atypical orphan carbohydrate-NRPS genomic island encodes a novel lytic transglycosylase.
abstract: Microbial genome sequencing platforms have produced a deluge of orphan biosynthetic pathways suspected of biosynthesizing new small molecules with pharmacological relevance. Genome synteny analysis provides an assessment of genomic island content, which is enriched in natural product gene clusters. Here we identified an atypical orphan carbohydrate-nonribosomal peptide synthetase genomic island in Photorhabdus luminescens using genome synteny analysis. Heterologous expression of the pathway led to the characterization of five oligosaccharide metabolites with lysozyme inhibitory activities. The oligosaccharides harbor a 1,6-anhydro-β-D-N-acetyl-glucosamine moiety, a rare structural feature for natural products. Gene deletion analysis and biochemical reconstruction of oligosaccharide production led to the discovery that a hypothetical protein in the pathway is a lytic transglycosylase responsible for bicyclic sugar formation. The example presented here supports the notion that targeting select genomic islands with reduced reliance on known protein homologies could enhance the discovery of new metabolic chemistry and biology.
authors.affiliation: Department of Chemistry, Yale University, New Haven, CT 06520, USA; Chemical Biology Institute, Yale University, West Haven, CT 06516, USA.
authors.forename: Xun
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Chemistry, Yale University, New Haven, CT 06520, USA; Chemical Biology Institute, Yale University, West Haven, CT 06516, USA; Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, CT 06510, USA. Electronic address: jason.crawford@yale.edu.
authors.forename: Jason M
authors.initials: JM
authors.lastname: Crawford
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D002686:Chitin / Q000737:chemistry / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D044404:Genomic Islands; D016695:Glycosyltransferases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D005810:Multigene Family; D009113:Muramidase / Q000037:antagonists & inhibitors / Q000378:metabolism; D009844:Oligosaccharides / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry; D010453:Peptide Synthases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D020637:Photorhabdus / Q000201:enzymology / Q000235:genetics; D021241:Spectrometry, Mass, Electrospray Ionization; D013379:Substrate Specificity
chemical_list: D009844:Oligosaccharides; D002686:Chitin; D016695:Glycosyltransferases; D009113:Muramidase; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase; D000117:Acetylglucosamine