Catalyzes the removal of elemental sulfur from cysteine to produce alanine (PubMed:18650437). It supplies the inorganic sulfur for iron-sulfur (Fe-S) clusters. May be involved in the biosynthesis of molybdenum cofactor (PubMed:18650437). [sulfur carrier]-H + L-cysteine = [sulfur carrier]-SH + L-alanine Kinetic parameter was determined for the protein lacking the 55 N-terminal amino acids and in a complex with LYRM4. Binds ISCU/NIFUN (PubMed:11060020). Forms a complex with LYRM4 (PubMed:18650437, PubMed:19454487). Interacts with HSPA9 (PubMed:26702583). Individual cells may vary AUG utilization in accordance with changes in metabolic status, the cytosolic pH being a strong determinant of this modulation. Predominantly expressed in heart and skeletal muscle. Also found in brain, liver and pancreas. The disease is caused by variants affecting the gene represented in this entry. Belongs to the class-V pyridoxal-phosphate-dependent aminotransferase family. NifS/IscS subfamily.