Catalyzes the transfer of a sulfur ion from a donor to cyanide or to other thiol compounds. Substrate preference is 3-mercaptopyruvate > thiosulfate. Involved in embryo and seed development. hydrogen cyanide + thiosulfate = 2 H(+) + sulfite + thiocyanate 2-oxo-3-sulfanylpropanoate + [thioredoxin]-dithiol = [thioredoxin]-disulfide + H(+) + hydrogen sulfide + pyruvate Expressed in roots, rosette and cauline leaves, stems, flowers and siliques. No visible phenotype under normal growth conditions.