Agmatine

Agmatine ((4-aminobutyl)guanidine, NH2-CH2-CH2-CH2-CH2-NH-C(-NH2)(=NH))
is the decarboxylation product of the amino acid arginine and is an
intermediate in polyamine biosynthesis. It is discussed as a putative
neurotransmitter. It is synthesized in the brain, stored in synaptic
vesicles, accumulated by uptake, released by membrane depolarization,
and inactivated by agmatinase. Agmatine binds to a2-adrenergic
receptor and imidazoline binding sites, and blocks NMDA receptors and
other cation ligand-gated channels. Agmatine inhibits nitric oxide
synthase (NOS), and induces the release of some peptide hormones.

http://en.wikipedia.org/wiki/Agmatine

Peptide

Peptides are the family of molecules formed from the linking, in a
defined order, of various amino acids. The link between one amino acid
residue and the next is an amide bond, and is sometimes referred to as
a peptide bond. An amide bond is somewhat shorter than a typical
carbon-nitrogen single bond, and has a partial double-bond character,
because the participating carbon molecule is doubly bonded to an oxygen
molecule and the nitrogen has a lone pair of electrons available for
bonding.

Peptides (like proteins) occur in nature and are responsible for a wide
array of functions, many of which are not yet understood. Antimicrobial
peptides generally disrupt the membranes of a target cell, causing
lysis of the cell. How this occurs, and what determines the activity
and selectivity of these peptides, is currently only known
approximately.

It has also beed documented that when certain food proteins such as
gluten, casein, egg protein and spinach protein are broken down, opioid
peptides are formed. These peptides mimick the effects of morphine, and
those who are unable to break them down will experience mental illness.
These peptides are quite short and are given names such as
casomorphine, gluten exorphine and dermorphine.

Peptides differ from proteins, which are also long chains of amino
acids, by virtue of their size. Traditionally, those peptide chains
that are short enough to make synthetically from the constituent amino
acids are called peptides rather than proteins. The dividing line is at
approximately 50 amino acids in length, since naturally-occurring
proteins tend, at their smallest, to be hundreds of residues long. So,
in essence, a peptide is a small protein.

Peptidomimetics (such as peptoids and ß-peptides) are molecules
related to peptides, but with different properties.

Decarboxylation

A Decarboxylation is any chemical reaction in which a carboxyl group
(-COOH) is split off from a compound as carbon dioxide (CO2).

Common biosynthetic decarboxylations of amino acids to amines are:

tryptophan to tryptamine, phenylalanine to phenylethylamine, tyrosine
to tyramine, histidine to histamine, serine to ethanolamine, glutamic
acid to GABA, lysine to cadaverine, arginine to agmatine, ornithine to
putrescine, 5-HTP to serotonin, and L-DOPA to dopamine.

Other decarboxylation reactions from the citric acid cycle include:

pyruvate to acetyl-CoA, oxalosuccinate to a-ketoglutarate, and
a-ketoglutarate to succinyl-CoA.

Enzymes that catalyze decarboxylations are called decarboxylases or,
more formally, carboxy-lyases (E.C.4.1.1).

Chemical decarboxylations reactions often require extensive heating in
high-boiling solvents. Copper salts are often added as catalysts. Also
the addition of catalytic amounts of cyclohexen-2-one has been reported
to catalyze the decarboxylation of amino acids. Decarboxylations are
especially easy for alpha-keto acids due to the formation of a cyclic
transitional state.