Stable
under ordinary conditions. Moisture,
light sensitive.
GENERAL
DESCRIPTION
Amino
Acid is any of the organic compounds in which one (or
more ) amino group (-NH2)
and one (or more ) carboxylic acid group (-COOH) are
both present with general formula R-CH(NH2)COOH
containing carbon, hydrogen, oxygen, nitrogen, and in
certain cases sulfur atoms. Two groups attached to the
same carbon (called the alpha-carbon atom at the end
of the compound) are polymerized to form peptides and
proteins. The amine group is protonated to form -NH3+
at low pH. The carboxylic acid group is deprotonated
to form -CO2-
at high pH. The carbon atom in the carboxyl group of
one amino acid binds covalently to the nitrogen atom
in the amino group of another amino acid to form a peptide
bond with the release of a water molecule. Proteins
are synthesized through the covalent chemical polypeptide
bonds. The sequence of these amino acids in the protein
polypeptides determines the shape, properties, and hence
biological role of the protein that function as chemical
messengers and as intermediates in metabolism. Proteins
are composed of various proportions of about 20 commonly
occurring amino acids. Plants or other biological systems
can synthesize amino acids from simple inorganic compounds,
but animals rely on adequate supplies in their diet.
More than 100 common amino acids occur in plants or
in other microorganic systems. The 20 amino acids commonly
found in animals are Alanine, Arginine, Asparagine,
Aspartic Acid, Cysteine, Glutamic Acid, Glutamine, Glycine,
Histidine, Isoleucine, Leucine, Lysine, Methionine,
Phenylalanine, Proline, Serine, Threonine, Tryptophan,
Tyrosine, and Valine. Many of the amino acids can be
synthesized in the human or animal body from other cellular
metabolites when needed (called Non-essential Amino
Acids). Animals are not able to synthesize some amino
acids necessary in metabolism in sufficient quantities.
It must therefore be present in the diet (called Essential
Amino Acids). In man, these essential amino acids are
Arginine, Histidine, Isoleucine, Leucine, Lysine, Methionine,
Phenylalanine, Threonine, Tryptophan and Valine. Proline is the only heterocyclic amino acid among twenty amino acids. Unlike
other amino acids, proline is readily soluble in alcohol. Proline is an imino
acid as it contains no amino group, nonetheless, it is called an amino acid. It
is found in essentially most proteins and is a major constituent in collagens,
the fibrous protein of connective tissue. Proline plays the important role to
determine the protein¡¯s structural shape when amino acids are incorporated into
them.