Genes Encoding Enzymes Responsible for Biosynthesis of L-Lyxose and Attachment of Eurekanate during Avilamycin Biosynthesis

Abstract

The oligosaccharide antibiotic avilamycin A is composed of a polyketide-derived dichloroisoeverninic acid moiety attached to a heptasaccharide chain consisting of six hexoses and one unusual pentose moiety. We describe the generation of mutant strains of the avilamycin producer defective in different sugar biosynthetic genes. Inactivation of two genes (aviD and aviE2) resulted in the breakdown of the avilamycin biosynthesis. In contrast, avilamycin production was not influenced in an aviP mutant. Inactivation of aviGT4 resulted in a mutant that accumulated a novel avilamycin derivative lacking the terminal eurekanate residue. Finally, AviE2 was expressed in Escherichia coli and the gene product was characterized biochemically. AviE2 was shown to convert UDP-D-glucuronic acid to UDP-D-xylose, indicating that the pentose residue of avilamycin A is derived from D-glucose and not from D-ribose. Here we report a UDP-D-glucuronic acid decarboxylase in actinomycetes.

Genetic dissection of the biosynthetic route to gentamicin A2by heterologous expression of its minimal gene set

“…Although NDP-ribose could not be tested because of its unavailability, these results provide evidence that UDP-D-xylose (UDP-Xyl) is a cofactor for gentamicin A 2 biosynthesis, and that its transfer to paromamine is catalyzed by GtmE. It was reported (27) that an UDP-glucuronic acid (UDP-GlcA) decarboxylase AviE2 was involved in the formation of UDP-Xyl in avilamycinproducing Streptomyces viridochromogenes Tu57 (27). CalS8 of calicheamicin-producing M. echinospora was reported as an UDP-Glc dehydrogenase involved in deoxypentose biosynthesis.…”

Natural‐Product Sugar Biosynthesis and Enzymatic Glycodiversification

“…[116] For the biosynthesis of the l-lyxose-derived moiety (107) of avilamycin in Streptomyces viridochromogenes, compound 9 is converted to UDP-d-xylose (10) by the short-chain dehydrogenase/reductase (SDR) enzyme AviE2, which is a UDP-glucuronate decarboxylase (or UDP-xylose synthase) homologue. [118] Compound 10 is the common xylose donor used in the biosynthesis of cell-wall polysaccharides in plants and fungi, cell-surface polysaccharides in bacteria, and for protein glycosylation in animals. Interestingly, with the exception of AviE2, enzymes catalyzing the formation of 10 have not been found in any other secondary metabolite biosynthetic pathways in actinomycetes.…”

The Active Conformation of Avilamycin A Is Conferred by AviX12, a Radical AdoMet Enzyme

“…In contrast, avilamycin biosynthesis starts with the formation of a disaccharide, and the polyketide moiety is attached to the hexasaccharide at the very end of the biosynthetic route. D-Mannose was discussed to be one component of the disaccharide starter molecule (11). Our data now indicate that the disaccharide is synthesized from D-glucose instead of D-mannose and that AviX12 is involved in C-2 epimerization of the glucose moiety after the whole avilamycin molecule is generated.…”

“…The next plausible steps toward formation of the heptasaccharide chain might be the unusual C1-C1 linkage between lyxose and mannose and subsequently the attachment of the eurekanate to the L-lyxose moiety. A knock-out mutation in aviE2, the gene encoding a UDP-glucuronic acid decarboxylase involved in the biosynthesis of lyxose from glucose, led to the breakdown of avilamycin A biosynthesis, confirming the presumption of the start of avilamycin biosynthesis in the coupling of lyxose and mannose (11). Inactivation of aviGT4, a putative glycosyltransferase, led to the formation of a new avilamycin derivative lacking the terminal eurekanate residue (11).…”