A search of the Cambridge structure database reveals around 18 high quality crystal structures containing this species are known, many as metal salts.
The article reports that “in the presence of sulfate radicals generated from peroxydisulfate, the (Krebs cycle) intermediates underwent 24 interconversion reactions” covering “the critical topology of the oxidative Krebs cycle, the glyoxylate shunt and the succinic-semialdehyde pathway“. The suggestion therefore is that these crucial metabolic reactions may have existed before life itself absorbed them into the oxidative Krebs cycle. The challenge now is to explain how or if the more ancient reductive Krebs cycle (which fixes carbon dioxide) might have arisen prebiotically. More exciting stuff to come I fancy.
- M.A. Keller, D. Kampjut, S.A. Harrison, and M. Ralser, "Sulfate radicals enable a non-enzymatic Krebs cycle precursor", Nature Ecology & Evolution, vol. 1, pp. 0083, 2017. http://dx.doi.org/10.1038/s41559-017-0083