Definition

1. Noun:
   • A crystalline amino acid found in proteins, especially keratin: Cystine is a sulfur-containing amino acid that occurs as a crystalline substance. It is a key structural component of many proteins, most notably keratin, which is found in hair, skin, and nails. It was historically discovered in bladder stones.

Usage

• Cystine is primarily used in biochemical and nutritional contexts to describe this specific amino acid and its role in protein structure and metabolism.
• It is often discussed in relation to protein chemistry, dietary requirements, and certain metabolic disorders.

Examples

• Noun:
  • The stability of hair is due in part to the disulfide bonds formed by cystine.
  • A diet deficient in cystine precursors can affect keratin production.
  • The analysis revealed a high concentration of cystine in the protein sample.

Advanced Usage

• "Cystine bridge" or "Disulfide bridge": A covalent bond formed between two cystine residues (from two cysteine molecules) that stabilizes the three-dimensional structure of proteins.
  • The antibody's function depends on the integrity of its cystine bridges.

Variants and Related Words

• Cysteine (noun): The reduced, sulfur-containing amino acid that is the precursor to cystine. Two cysteine molecules oxidize to form one cystine molecule.
• Cystinuria (noun): A hereditary metabolic disorder characterized by the excessive excretion of cystine in the urine, often leading to kidney stone formation.

Synonyms

• Amino acid: The general class of organic compounds to which cystine belongs. (Note: This is a broader category, not a direct synonym.)

Notes

• Cystine is not one of the 20 standard amino acids encoded by DNA for direct protein synthesis. Instead, it is formed when two cysteine molecules (which are encoded) become linked via an oxidation reaction, creating a disulfide bond. This bond is crucial for the strength and rigidity of many structural proteins.

Noun

1. a crystalline amino acid found in proteins (especially keratin); discovered in bladder stones