 The body produces reactive sulfur species, known as persulfides and polysulfides, through the action of certain enzymes. These compounds play important roles in cellular regulation, such as energy metabolism and redox signaling. Recent studies have suggested that three enzymes, cystinal tRNA synthetase, CARs, three mercaptopiravate sulfur transferase, three MST, and cystathionine beta synthase, CBS, may also contribute to the production of these compounds. However, recent research has shown that CARs is the primary source of reactive persulfides and polysulfides in mammalian cells. This article was authored by Camryl Hafez Zainal Abidine, Tamoki Aida, Massinobo Morita, and others.