n.
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.
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.