What does "cysteine" mean?

A sulphur-containing nonessential amino acid C₃H₇NO₂S found in most animal proteins; it readily oxidizes to cystine.

How do you pronounce "cysteine"?

Pronounced //ˈsɪs.təˌiːn//.

Common synonyms include: amino acid, cys, cys when viewed as a monomer in proteins, e910, e910 when used as a food additive, e920.

//ˈsɪs.təˌiːn// noun

noun ·Uncommon ·Advanced level

Noun

1
A sulphur-containing nonessential amino acid C₃H₇NO₂S found in most animal proteins; it readily oxidizes to cystine. countable, uncountable
2
an amino acid containing sulfur that is found in most proteins; oxidizes on exposure to air to form cystine wordnet

An alteration of cystine, see -eine.

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.