C₃₅ Hopanoid Side Chain Biosynthesis: Reduction of Ribosylhopane into Bacteriohopanetetrol by a Cell‐Free System Derived from Methylobacterium organophilum

Abstract

The major bacterial triterpenoids of the hopane series each consist of a C30 triterpene hopane moiety and an additional nonterpene C5 side chain derived from D-ribose and linked through its C-5 carbon atom to the hopane side chain. Bacteriohopanetetrol and aminobacteriohopanetriol are the most common representatives of this natural product series, adenosylhopane and ribosylhopane being putative precursors. Deuterium-labelled ribosylhopane was obtained by hemisynthesis and converted into deuterium-labelled bacteriohopanetetrol in the presence of NADPH, thus giving evidence of this as yet unknown precursor-to-product relationship in the bacterial hopanoid metabolic pathway.

Hopanoid-free Methylobacterium extorquens DM4 overproduces carotenoids and has widespread growth impairment

“…It remains unresolved whether these are biosynthetic by-products or whether this biosynthetic pathway is tightly regulated by the bacterium to produce a specific suite of products, each with different function. Recent work on expressing hopanoid genes in a cell-free system derived from Methylobacterium organophilum has begun to shed light on the function of these genes [48]. The wide range of hopanoid structures suggests the possibility that they serve a wide range of functions; this is consistent with biophysical evidence suggesting a diversity of functional roles [49].…”

Biosynthesis of Isoprene Units in Euphorbia lathyris Laticifers vs. Other Tissues: MVA and MEP Pathways, Compartmentation and Putative Endophytic Fungi Contribution

“…To check the possible deuterium incorporation in the isoprene units, gas chromatography-isotope ratio mass spectrometry (IR GC-MS), a quite sensitive method, was utilized, allowing determination of the 2 H content by measuring the δ 2 H (‰) values of individual compounds corresponding to the deviation of the 2 H/ 1 H ratios relative to that of an universal reference sample [43,44]. This method for deuterium detection proved to be efficient in labeling experiments with a deuteriated precursor for the biosynthesis of bacterial triterpenes of the hopane series [45]. Results are consistent with those obtained after incorporation of (2- 13 C)MVA.…”

Determination of the δ2H values of high molecular weight lipids by high‐temperature gas chromatography coupled to isotope ratio mass spectrometry

“…Therefore, only very few larger compounds (eluting later than a C 36 n ‐alkane on an apolar stationary phase) have had their δ 2 H values successfully determined. Existing measurements were achieved by implementing long isothermal holds at 320°C but only with highly purified and 2 H‐labelled compounds, 29 due to the low GC resolution and δ 2 H precision associated with this methodology.…”

“…This setup requires analytes to be GC-amenable, 28 limiting analyses to compounds of a molecular weight and polarity low enough to elute at a typical maximum capillary column operating temperature of 320 C. Therefore, only very few larger compounds (eluting later than a C 36 n-alkane on an apolar stationary phase) have had their δ 2 H values successfully determined. Existing measurements were achieved by implementing long isothermal holds at 320 C but only with highly purified and 2 H-labelled compounds, 29 due to the low GC resolution and δ 2 H precision associated with this methodology. However, the δ 2 H values of large and/or polar compounds can be of significant interest.…”