title: Sulfoquinovose in the biosphere: occurrence, metabolism and functions.
abstract: The sulfonated carbohydrate sulfoquinovose (SQ) is produced in quantities estimated at some 10 billion tonnes annually and is thus a major participant in the global sulfur biocycle. SQ is produced by most photosynthetic organisms and incorporated into the sulfolipid sulfoquinovosyl diacylglycerol (SQDG), as well as within some archaea for incorporation into glycoprotein N-glycans. SQDG is found mainly within the thylakoid membranes of the chloroplast, where it appears to be important for membrane structure and function and for optimal activity of photosynthetic protein complexes. SQDG metabolism within the sulfur cycle involves complex biosynthetic and catabolic processes. SQDG biosynthesis is largely conserved within plants, algae and bacteria. On the other hand, two major sulfoglycolytic pathways have been discovered for SQDG degradation, the sulfo-Embden-Meyerhof-Parnas (sulfo-EMP) and sulfo-Entner-Doudoroff (sulfo-ED) pathways, which mirror the major steps in the glycolytic EMP and ED pathways. Sulfoglycolysis produces C3-sulfonates, which undergo biomineralization to inorganic sulfur species, completing the sulfur cycle. This review discusses the discovery and structural elucidation of SQDG and archaeal N-glycans, the occurrence, distribution, and speciation of SQDG, and metabolic pathways leading to the biosynthesis of SQDG and its catabolism through sulfoglycolytic and biomineralization pathways to inorganic sulfur.
authors.affiliation: ACRF Chemical Biology Division, The Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria 3052, Australia.|Department of Medical Biology, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Ethan D
authors.initials: ED
authors.lastname: Goddard-Borger
authors.affiliation: School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia.
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
mesh_terms: D001105:Archaea / Q000378:metabolism; D000458:Cyanobacteria / Q000378:metabolism; D003580:Cytochromes / Q000737:chemistry / Q000378:metabolism; D005964:Glucosyltransferases / Q000737:chemistry / Q000378:metabolism; D006017:Glycolipids / Q000737:chemistry / Q000378:metabolism*; D008055:Lipids / Q000737:chemistry; D053858:Metabolic Networks and Pathways; D008757:Methylglucosides / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D010788:Photosynthesis / Q000502:physiology; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry / Q000502:physiology*; D010944:Plants / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D020524:Thylakoids / Q000737:chemistry / Q000378:metabolism*
chemical_list: D003580:Cytochromes; D006017:Glycolipids; D008055:Lipids; D008757:Methylglucosides; D045322:Photosynthetic Reaction Center Complex Proteins; C015518:sulfolipids; C013694:sulfoquinovosyl diglyceride; C009358:sulfoquinovose; D013455:Sulfur; D005964:Glucosyltransferases; C492484:UDP-sulfoquinovose synthase, Chlamydomonas reinhardtii
keywords: chloroplasts; glycolipids; photosynthesis; sulfoglycolysis; sulfolipid; sulfur cycle