-ˌdēn, -_də̇n noun
also his·ti·din -_də̇n
( -s )
Etymology: International Scientific Vocabulary hist- + -idine, -idin; originally formed as German histidin
: a crystalline basic amino acid C 3 H 3 N 2 CH 2 CH(NH 2 )COOH that is essential in the nutrition of the rat, is synthesized by microorganisms and by plants, and is formed by the decomposition of most proteins (as globin); 4(or 5)-imidazole-alanine