HOOCCHNH2CH2SH

HOOCCHNH2CH2SH is the chemical formula for L-cysteine. L-cysteine is a proteinogenic amino acid, meaning it is one of the twenty standard amino acids that make up proteins in living organisms. Its chemical structure features a thiol group (-SH) attached to a methylene group (-CH2-) which is in turn bonded to the alpha-carbon. The alpha-carbon is also bonded to a carboxyl group (-COOH) and an amino group (-NH2). The 'L' designation refers to its stereochemistry, indicating its configuration is the same as L-glyceraldehyde.

This amino acid is semi-essential, as the human body can synthesize it, but often requires dietary intake to meet its needs. The thiol group is particularly reactive and plays a crucial role in protein structure through disulfide bond formation, linking different parts of a polypeptide chain or stabilizing tertiary structures. L-cysteine is also a precursor to glutathione, a major antioxidant in cells. It is found in many protein-rich foods such as meat, poultry, eggs, and dairy products. Industrially, it is often obtained from the hydrolysis of feathers or hair.