Comparative metabolomic analysis of an alternative biosynthetic pathway to pseudosugars in Actinosynnema mirum DSM 43827

Abstract

Through a combination of genome mining, gene knockouts, and comparative metabolomic studies, a new biosynthetic pathway to validoxylamine A has been discovered in Actinosynnema mirum DSM 43827. The study revealed the rich diversity of biosynthetic pathways to pseudosugar-containing natural products.

Keywords: Actinosynnema mirum; metabolism; natural products; pseudoglycosyltransferase; pseudosugar; validoxylamine A.

Figure 1

Genetic organization of pseudo-oligosaccharide biosynthetic gene clusters in various organisms. A) the validamycin cluster in S. hygroscopicus subsp. limoneus. B) the validamycin cluster in S. hygroscopicus subsp. jinggangensis 5008. C) the cryptic gene cluster in Actinosynnema mirum that contains PsGT (amir_1997) and EVS (amir_2000) genes.

Figure 2

Statistical comparative metabolomic analysis of A. mirum wild-type, ΔPsGT and EVS::apr^R mutants. A) PCA-DA scores plot of A. mirum wild-type (n5), ΔPsGT mutant (n5), and EVS::apr^R mutant (n5) (DA1DA2, 70% of variance). Analysis is on the basis of polar metabolites detected in positive ion mode. B) Volcano plot of polar metabolites from A. mirum wild-type, ΔPsGT mutant, and EVS::apr^R mutant detected in positive ion mode. Log 10 (fold change) values are on the basis of average (n 5/group) responses calculated by MarkerView^™ software.

Scheme 1

Biosynthetic pathways to acarbose and validamycin A, and a proposed alternative pathway to validoxylamine A in A. mirum. Reaction steps from valienone 7-phosphate to validoxylamine A in A. mirum are expected to be the same as those in S. hygroscopicus.