phenylalanine[fen′əl al′ə nēn′, fē′nəl-]
an essential amino acid, CHCHCH(NH)COOH, occurring in proteins
An essential amino acid, C9H11NO2, that occurs as a constituent of many proteins and is normally converted to tyrosine in the human body. It is necessary for growth in infants and for nitrogen equilibrium in adults.
(countable and uncountable, plural phenylalanines)