alpha-amino acid

n.
  1. Any of the 20 or so amino acids that has the amino and carboxyl groups attached to the same carbon atom, usually has an l-configuration, and is the chemical constituent of a protein.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.