Glycine origin of the methyl substituent on C7′-N of octodiose for the biosynthesis of apramycin

Abstract

Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonine, to the Streptomyces tenebrabrius UD2 fermentation medium substantially increases the production of apramycin with little effect on the growth of mycelia, indicating that glycine and/or serine might be involved in the biosynthesis of apramycin. The 13C-NMR analysis of [2-13C] glycine-fed (25% enrichment) apramycin showed that glycine specifically and efficiently incorporated into the only N-CH3 substituent of apramycin on the C7' of the octodiose moiety. We noticed that the in vivo concentration of S-adenosyl methionine increased in parallel with the addition of glycine, while the addition of methione in the fermentation medium significantly decreased the productivity of apramycin. Therefore, the methyl donor function of glycine is proposed to be involved in the methionine cycle but methionine itself was proposed to inhibit the methylation and methyl transfer processes a previously reported for the case of rapamycin. The 15N NMR spectra of [2-13C,15N]serine labeled apramycin indicated that serine may also act as a limiting precursor contributing to the -NH2 substituents of apramycin.

Biosynthetic Origin of the Octose Core and Its Mechanism of Assembly during Apramycin Biosynthesis

“…However, only two genes in apr are annotated as encoding a transaminase (i.e., AprS and AprL), and both have already been assigned other functions. The alternative hypothesis is that C7′ and C8′ of 1 are derived from an amino acid such as glycine or a derivative thereof (Figure , path B) . However, early feeding experiments revealed that neither glycine nor serine is a precursor of carbon source to apramycin …”

“…The alternative hypothesis is that C7′ and C8′ of 1 are derived from an amino acid such as glycine or a derivative thereof (Figure 2, path B). 29 However, early feeding experiments revealed that neither glycine nor serine is a precursor of carbon source to apramycin. 29 Recent results, however, have suggested a third possibility.…”

“…29 However, early feeding experiments revealed that neither glycine nor serine is a precursor of carbon source to apramycin. 29 Recent results, however, have suggested a third possibility. In particular, 7′-N-acetyl-demethylaprosamine (7) accumulates in the fermentation media when aprU is deleted, and AprU has been shown to catalyze C5-phosphorylation of 7 to yield 8 (Figure 1).…”

Anticancer property of sediment actinomycetes against MCF–7 and MDA–MB–231 cell lines

“…Many of the antitumor compounds from marine drugs are derived from algal metabolites [3] and these metabolites play an important role in identification of new pharmaceutical compounds [4,5] . Actinomycetes are one of the most important sources for new bioactive compounds such as antibiotics and enzymes [6][7][8] which have diverse clinical effects against many pathogenic organisms viz., bacteria, fungi and parasite, etc. In fact, more than 60% of approved drugs are derived from natural compounds [9] in that, 50% of the natural antibiotics are produced from actinomycetes, among them marine actinomycetes have been reported to have antifungal, antibacterial and antiinflammatory activities [10] .…”