L-cystine is known as a semi-essential amino acid as it is formed directly from L-methionine. Its functions aid in the detoxification of sulphuric acid when combined with glycine and glutamic acid. There is also evidence of anti inflammatory properties (1).
1 – Fiorucci, S., Antonelli, E., Distrutti, E., Rizzo, G., Mencarelli, A., Orlandi, S., … & Wallace, J. L. (2005). Inhibition of hydrogen sulfide generation contributes to gastric injury caused by anti-inflammatory nonsteroidal drugs. Gastroenterology,129(4), 1210-1224.