The element sulfur is essential for life. In the biosphere, sulfur is distributed into a wide range of organosulfur species that by definition contain a carbon-sulfur bond. It is estimated that up to half of all organosulfur in the biosphere resides within the organosulfur sulfolipid sulfoquinovosyl diacylglyceride (SQDG), which is produced by all photosynthetic organisms. The annual production of sulfoquinovose (SQ; 6-deoxy-6-sulfo-d-glucose), the sulfosugar headgroup of SQDG, is estimated at 10 billion tonnes per annum. The degradation of SQ releases ATP, reducing power as NAD(P)H, sulfur- and carbon-based building blocks, and inorganic sulfur (sulfite), contributing to the global biogeochemical sulfur cycle. Biodegradation of SQ occurs in two tiers: sulfoglycolysis involving breakdown of SQ to short-chain (2- and 3-carbon) organosulfonates) followed by biomineralization (breakdown of short-chain organosulfonates to sulfite). In contrast to well-characterised sulfoglycolysis pathways, the biomineralization pathways of short-chain organosulfonates are poorly understood.
Here we present work towards the characterisation of the first three enzymes, HpsNOP, in the biomeralization pathway of 3-carbon organosulfonate, 2,3-dihydroxypropane-1-sulfonate (DHPS) from Cupriavidus pinatubonensis JMP134. Our preliminary results include enzyme kinetics and crystal structures of HpsO. We will discuss our new findings that redefine the previously proposed roles of these enzymes, substrate preference, and stereospecificity.