Protein Architecture—Amino AcidsPro

Protein Architecture—Amino Acids
Proteins are polymers of amino acids, with each amino
acid residue joined to its neighbor by a specific type
of covalent bond. (The term “residue” reflects the loss
of the elements of water when one amino acid is joined
to another.) Proteins can be broken down (hydrolyzed)
to their constituent amino acids by a variety of methods,
and the earliest studies of proteins naturally focused on the free amino acids derived from them. Twenty different amino acids are commonly found in proteins. The
first to be discovered was asparagine, in 1806. The last
of the 20 to be found, threonine, was not identified until
1938. All the amino acids have trivial or common names,
in some cases derived from the source from which they
were first isolated. Asparagine was first found in asparagus, and glutamate in wheat gluten; tyrosine was
first isolated from cheese (its name is derived from the
Greek tyros, “cheese”); and glycine (Greek glykos,
“sweet”) was so named because of its sweet taste.