Serotonin N-acetyl transferase also known as arylalkylamine N-acetyltransferase

Aralkylamine N-acetyltransferase

In enzymology, an aralkylamine N-acetyltransferase is an enzyme that catalyzes the chemical reactionThus, the two substrates of this enzyme are acetyl-CoA and 2-arylethylamine, whereas its two products are CoA and N-acetyl-2-arylethylamine....

or AANAT is a protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 that, in humans, is encoded by the AANAT gene

Gene

A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

.

Function

The protein encoded by this gene is an enzyme involved in the conversion of serotonin

Serotonin

Serotonin or 5-hydroxytryptamine is a monoamine neurotransmitter. Biochemically derived from tryptophan, serotonin is primarily found in the gastrointestinal tract, platelets, and in the central nervous system of animals including humans...

 to melatonin

Melatonin

Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...

 in pinealocyte

Pinealocyte

Pinealocytes are the main cells of the pineal gland. They produce and secrete melatonin. Pinealocytes have an organelle called the synaptic ribbon; this is considered to be a specific marker for pinealocytes...

s. It is an acetyl-CoA-dependent enzyme of the GCN5-related family of N-acetyltransferase

N-Acetyltransferase

N-acetyltransferase is an enzyme that catalyzes the transfer of acetyl groups from acetyl-CoA to arylamines. They have wide specificity for aromatic amines, particularly serotonin, and can also catalyze acetyl transfer between arylamines without CoA. EC 2.3.1.5....

s (GNATs).

Arylalkylamine N-acetyltransferase is the penultimate enzyme in melatonin synthesis and controls the night/day rhythm in melatonin production in the vertebrate pineal gland. Melatonin is essential for seasonal reproduction, modulates the function of the circadian clock in the suprachiasmatic nucleus, and influences activity and sleep. This enzyme is rapidly inactivated when animals are exposed to light at night. This protein is 80% identical to sheep and rat AA-NAT. Arylalkylamine N-acetyltransferase may contribute a multifactorial genetic diseases such as altered behavior in sleep/wake cycle.

Structure

This family shares four conserved sequence motifs designated A-D. Motif B serves as the location of the serotonin binding slot. The structure of Serotonin N-acetyl transferase was determined by X-ray diffraction(XRD). A resolution of 1.80 angstroms was obtained. The structural weight is 24121.55 daltons. It is a polypeptide with a length of 207 residues. The secondary structure consists of alpha helices and beta sheets. It is 28% helical (10 helices;60 residues) and 23% beta sheet (9 strands;48 residues).