Thiosulfate:glutathione sulfurtransferase (TST) required to produce S-sulfanylglutathione (GSS(-)), a central intermediate in hydrogen sulfide metabolism (PubMed:24981631). Provides the link between the first step in mammalian H(2)S metabolism performed by the sulfide:quinone oxidoreductase (SQOR) which catalyzes the conversion of H(2)S to thiosulfate, and the sulfur dioxygenase (SDO) which uses GSS(-) as substrate (PubMed:24981631). The thermodynamic coupling of the irreversible SDO and reversible TST reactions provides a model for the physiologically relevant reaction with thiosulfate as the sulfane donor (PubMed:24981631). glutathione + thiosulfate = H(+) + S-sulfanylglutathione + sulfite GSS(-) is a potent inhibitor of TSTD1, since the presence of the sulfur dioxygenase (SDO) strongly increases the TSTD1 catalytic activity (PubMed:24981631). Localized around the nuclear membranes. Highly expressed in kidney, liver and skeletal muscle. Lower levels of expression in heart, colon, thymus, spleen, placenta and lung. Weakly expressed in brain, small intestine and peripheral blood leukocytes. Expressed at high levels in the breast carcinoma cell lines MCF-7 and MDA-MB-468 and at a lower level in the breast carcinoma cell line MDA-MB-231, the colon carcinoma call line LoVo and the lung carcinoma cell line A-549. No expression in the cell lines EFO-27 and HeLa, or the normal breast tissue cell lines MCF-10A and H184A1. Detected in invasive ductal carcinoma, but not in the adjacent tissues.