L-Cysteine Publisher



Sameem B^{1, 2, 3} ; Khan F^{1, 2, 3} ; Niaz K^{1, 2, 3}
Source: Nonvitamin and Nonmineral Nutritional Supplements Published:2018

Abstract

L-cysteine is a proteingenic amino acid, which contributes toward a multitude of functions in biological systems. Cysteine is classified as a semiessential amino acid and can be synthesized in the liver from methionine, which is a sulfur-containing amino acid. This makes the abundance of methionine a critical factor to human health. As a building block, l-cysteine contributes 2% of the total structural proteins in the body in the form of connective tissue, cell membranes, and the myelin sheaths around neurons, structures, which protect neurons from oxidative stress and harsh environmental conditions. The stiffness of the connective tissue neutralizes heavy metals in the body. l-cysteine is a hydrophilic amino acid, possesses a thiol moiety which contributes toward its antioxidative properties, and has a high reactivity and affinity for heavy metals like mercury (Hg), leading to their excretion/detoxification from the body (Jan et al., 2015). It is given as a supplement in the form of precursor called N-acetyl-l-cysteine (NAC). The body synthesizes glutathione (GSH) from cysteine; the former is a powerful antioxidant, toxin/radical scavenger. Glutathione (GHS) stimulates the production of leukotriene which is a key element in the body’s defense system, inhibits inflammatory processes, and boosts the immune system. Studies have revealed that NAC can be helpful in treating many health problems like osteoporosis, acute respiratory diseases, and acetaminophen poisoning. In this chapter, we highlighted the structure, biochemistry, bioavailability, sources, possible interactions with drugs, foods, and other supplements, and health effects of l-cysteine. © 2019 Elsevier Inc. All rights reserved.