A patchwork pathway for catabolism of the sulfosugar sulfofucose

Abstract

AbstractWe report the isolation ofParacoccus onubensisstrain Merri, which can grow on the rare sulfosugar sulfofucose (6-deoxy-6-sulfo-D-galactose) as sole carbon source, leading to its breakdown and release of sulfite. Genome sequencing and comparative proteomics of samples grown on glucose versus sulfofucose identified a genetic locus containing most of the genes for a sulfoglycolytic pathway for breakdown of sulfofucose to the 3-carbon organosulfonate sulfolactaldehyde, and a biomineralization pathway for catabolism of sulfolactaldehyde to pyruvate and sulfite. A candidate sulfotagatose-1-phosphate aldolase was expressed and was active on the epimeric substrate sulfofructose-1-phosphate. Its 3D X-ray structure revealed a close homology to sulfofructose-1-phosphate aldolase from the sulfoglycolytic Embden-Meyerhof-Parnas pathway. A patchwork sulfofucose catabolism pathway is proposed involving a sulfofucolytic Embden-Meyerhof-Parnas and short-chain organosulfonate biomineralization pathway.SignificanceSulfosugars are important compounds in the biogeochemical sulfur cycle and are produced by a wide range of photosynthetic plants, algae and cyanobacteria. While the pathways for the biosynthesis and catabolism of sulfoquinovose are well studied, much less is known about the rarer sulfosugar sulfofucose. We report a bacterium that can use sulfofucose as sole carbon source and achieve its complete breakdown to produce sulfite. We propose that sulfofucose catabolism is achieved using enzymes of the sulfoglycolytic Embden-Meyerhof-Parnas pathway that tolerate a change in stereochemistry at C4 of the sulfosugar. The sulfolactaldehyde output of this pathway is broken down to sulfite through a biomineralization pathway via sulfolactate. Microbial metabolism of this rare sulfosugar can be achieved through repurposing enzymes within known sulfosugar and short-chain organosulfonate catabolism catabolism.