Riboneogenesis in Yeast

Abstract

Summary Gluconeogenesis converts three carbon units into glucose. Here we identify an analogous pathway in Saccharomyces cerevisiae for converting three carbon units into ribose, a component of nucleic acids and nucleotides. This riboneogenic pathway involves the enzyme sedoheptulose-1,7-bisphosphatase (SHB17), whose activity was identified based on accumulation of sedoheptulose-1,7-bisphosphate in the corresponding knockout strain. We determined the crystal structure of Shb17 in complex with sedoheptulose-1,7-bisphosphate, and found that the sugar is bound in the closed furan form in the active site. Like fructose-1,6-bisphosphate, sedoheptulose-1,7-bisphosphate is produced by aldolase, in this case from erythrose 4-phosphate and dihydroxyacetone phosphate. Hydrolysis of sedoheptulose-1,7-bisphosphate by SHB17 provides an energetically favorable input to the non-oxidative pentose phosphate pathway to drive ribose production. Flux through SHB17 is enhanced under conditions when ribose demand is high relative to demand for NADPH, including during ribosome biogenesis in metabolically synchronized yeast cells. Thus, riboneogenesis provides a thermodynamically-driven route of ribose production uncoupled from formation of NADPH.

Inhibition of Nicotinamide Phosphoribosyltransferase (NAMPT), an Enzyme Essential for NAD+ Biosynthesis, Leads to Altered Carbohydrate Metabolism in Cancer Cells

“…To confirm the identity of these enzymatic products, we showed that the fructose 1-phosphate formed exhibited a retention time and MS/MS spectra identical to those of the standard of fructose 1-phosphate. Similarly, the sedoheptulose 1-phosphate synthesized was also shown to exhibit a retention time and MS/MS spectra identical to those previously reported (29). In addition, these products exhibited retention times and MS/MS spectra identical to those FIGURE 2.…”

“…Fructose 1-phosphate formed from the enzymatic reaction exhibited the same retention time and MS/MS spectra as the commercial standard (fructose 1-phosphate). Sedoheptulose 1-phosphate synthesized using the two different methods also exhibited the same retention times and MS/MS spectra as reported previously (29). The commercial standard of fructose 1-phosphate was used for quantification of the endogenous metabolic intermediates.…”

“…The products formed were confirmed by LC-MS/MS analysis. The structural identification of sedoheptulose 1-phosphate from the aldolase reactions has been reported previously (29). Fructose 1-phosphate formed from the enzymatic reaction exhibited the same retention time and MS/MS spectra as the commercial standard (fructose 1-phosphate).…”

Characterization of Fructose 1,6-Bisphosphatase and Sedoheptulose 1,7-Bisphosphatase from the Facultative Ribulose Monophosphate Cycle Methylotroph Bacillus methanolicus

“…The reactions of SBA and SBPase are characteristic of the regeneration part of the Calvin cycle in photosynthetic organisms (11), and overproduction of SBPase in tobacco was shown to enhance carbon assimilation and crop yield (12). Recently, Saccharomyces cerevisiae was shown to possess a promiscuous SBPase encoded by SHB17, which also has FBPase and octulose-bisphosphatase (OBPase) activity and operates in the riboneogenesis pathway (13). It is possible that a promiscuous bisphosphate aldolase is active as both FBA and SBA and also that a bisphosphatase active as FBPase and SBPase exists.…”

An Evaluation of Acute Hydrogen Sulfide Poisoning in Rats through Serum Metabolomics Based on Gas Chromatography-Mass Spectrometry

“…11) Metabolomics is a scientific study that aims to identify and quantify the levels of all metabolites; it has been applied widely in many areas, such as medicine, biology, and food science. [12][13][14][15] GC-MS is an analytic method used frequently in metabolomics studies to examine low-molecular-weight metabolites, because GC-MS provides heightened equipment stability and user-friendly tools for data analysis. 16,17) This paper evaluates, through the use of GC/ MS-based metabolomics, the effect of acute hydrogen sulfide poisoning on the metabolic profiles of rats.…”