Biosynthesis of the polyoxins, nucleoside peptide antibiotics. Glutamate as an origin of 2-amino-2-deoxy-L-xylonic acid (polyoxamic acid)

Abstract

The biosynthetic origin of the carbon skeleton of 2-amino-2-deoxy-L-xylonic acid (polyoxamic acid) is described. This aminoaldonic acid is the N terminus of the nucleoside peptide antibiotics, the polyoxins, produced by Streptomyces cacaoi var. asoensis. In vivo experiments concerning incorporation and distribution of radioactivity from a number of 14C-labeled compounds have clearly shown that the carbon skeleton of glutamate is a precursor for this aminoaldonic acid and sugars are incorporated only after their conversion into gluamate through the glycolytic and the tricarboxylic acid cycle pathways. Experiments utilizing [14C]-acetate and succinate have also indicated multiple passages through the Krebs cycle are operating before their incorporation into polyoxamic acid via glutamate. The distribution of 14C between C-1 and C-5 of polyoxamic acid from [5-14C]glutamate experiment has indicated that 40% of glutamate incorporated only after the reversible conversion into alpha-ketoglutarate followed by the passage through the Krebs cycle. Lack of incorporation of 3H in the [1-14C;2-3H]- and [5-14C;2-3H]glutamate experiments is discussed in terms of a reaction(s) between glutamate and polyoxamic acid.

Characterization of the Polyoxin Biosynthetic Gene Cluster from Streptomyces cacaoi and Engineered Production of Polyoxin H

“…Moreover, the fragmentation pattern of the PolO-catalyzed product conformed well with that of the positive control sample prepared by cell-free enzyme solution (supplemental Fig. S9) (34). Thus, all of these results unambiguously characterized PolO as a distinctive AHV O-carbamoyltransferase.…”

“…The intermediates in the putative pathway for CPOAA biosynthesis were also proposed by feeding experiments with isotope-labeled substrates (34,37). The initial reaction involves reduction of L-glutamate to L-glutamate-␥-semialdehyde and then to AHV, which is further catalyzed to ACV by transcarbamoylation, followed by the final conversion into carbamoylpolyoxamic acid after hydroxylation.…”

Deciphering Carbamoylpolyoxamic Acid Biosynthesis Reveals Unusual Acetylation Cycle Associated with Tandem Reduction and Sequential Hydroxylation

“…The biosynthetic origin of CPOAA has been verified by labeling studies to be derived from L-glutamate (Funayama and Isono, 1975). In our previous study, five genes (polL, polM, polN, polO, polP) were preliminarily defined to be essential for CPOAA biosynthesis ( Figure 1C), and the initial two steps catalyzed by PolN (amino acid N-acetyltransferase) and PolP (acetylglutamate kinase) were revealed to be identical to those in arginine pathway (Chen et al, 2013).…”

Genetic dissection of the polyoxin building block-carbamoylpolyoxamic acid biosynthesis revealing the “pathway redundancy” in metabolic networks

“…Previous experiments assigned the biosynthetic precursors for the three building blocks (nucleoside skeleton, POIA and CPOAA) of polyoxin as UMP, L-isoleucine and L-glutamate, respectively [2,9,18-20]. As for CPOAA biosynthesis, the former labeling results led to a proposal that the biosynthesis was initiated by catalyzing L-glutamate to produce L-glutamate-γ-semialdehyde, which was finally converted to CPOAA with stepwise reactions [19,21]. …”