L-Cysteine yana daya daga cikin amino acid guda 20 na halitta kuma, banda methionine, wanda kawai ya ƙunshi sulfur.Amino acid ne wanda ba shi da mahimmanci wanda ke ɗauke da thiol wanda ke da oxidized don samar da Cystine.Yana da amino acid mai sulfur wanda ba shi da mahimmanci a cikin mutane, wanda ke da alaƙa da cystine, Cysteine yana da mahimmanci don haɓakar furotin, detoxification, da ayyuka daban-daban na rayuwa.An samo shi a cikin beta-keratin, babban furotin a cikin kusoshi, fata, da gashi, Cysteine yana da mahimmanci wajen samar da collagen, da kuma elasticity na fata da laushi.