In enzymology, a thiosulfate-dithiol sulfurtransferase (EC 2.8.1.5) is an enzyme that catalyzes the chemical reaction

thiosulfate + dithioerythritol ${\displaystyle \rightleftharpoons }$ sulfite + 4,5-cis-dihydroxy-1,2-dithiacyclohexane (i.e. oxidized dithioerythritol) + sulfide

Thus, the two substrates of this enzyme are thiosulfate and dithioerythritol, whereas its 3 products are sulfite, 4,5-cis-dihydroxy-1,2-dithiacyclohexane, and sulfide.

This enzyme belongs to the family of transferases, specifically the sulfurtransferases, which transfer sulfur-containing groups. The systematic name of this enzyme class is thiosulfate:dithioerythritol sulfurtransferase. Other names in common use include thiosulfate reductase, and TSR. This enzyme participates in sulfur metabolism.

• Schmidt A, Erdle I, Gamon B (1984). "Isolation and characterization of thiosulfate reductases from the green alga Chlorella fusca". Planta. 162: 243–249. doi:10.1007/BF00397446. PMID 24253096.