Histidine decarboxylase
Encyclopedia
Histidine decarboxylase (HDC) is the enzyme
that catalyzes the reaction that produces histamine
from histidine
with the help of vitamin B6 as follows:
C6H9N3O2
→ C5H9N3
+ CO2
In humans, the histidine decarboxylase enzyme is encoded by the HDC gene
.
The biogenic amine
histamine is an important modulator of numerous physiologic processes, including neurotransmission
, gastric acid secretion, and smooth muscle tone. The biosynthesis of histamine from histidine is catalyzed by the enzyme L-histidine decarboxylase. This homodimeric enzyme is a pyridoxal phosphate (PLP)-dependent decarboxylase and is highly specific for its histidine substrate.
Some mutations in the gene for this enzyme can cause symptoms of Tourette syndrome
; however, these mutations have only been observed in one family and are not thought to account for most cases of Tourette syndrome.
In bacteria
, it is synthesised as a proenzyme, PI. Cleavage
of the proenzyme PI chain yields two subunits, alpha and beta, which arrange as a hexamer
, (alpha beta)6, by nonhydrolytic self-catalysis.
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that catalyzes the reaction that produces histamine
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
from histidine
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
with the help of vitamin B6 as follows:
C6H9N3O2
Histidine
Histidine Histidine, an essential amino acid, has a positively charged imidazole functional group. It is one of the 22 proteinogenic amino acids. Its codons are CAU and CAC. Histidine was first isolated by German physician Albrecht Kossel in 1896. Histidine is an essential amino acid in humans...
→ C5H9N3
Histamine
Histamine is an organic nitrogen compound involved in local immune responses as well as regulating physiological function in the gut and acting as a neurotransmitter. Histamine triggers the inflammatory response. As part of an immune response to foreign pathogens, histamine is produced by...
+ CO2
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
In humans, the histidine decarboxylase enzyme is encoded by the HDC 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...
.
The biogenic amine
Biogenic amine
-Examples:Some prominent examples of biogenic amines include:* Histamine - a substance derived from the amino acid histidine that acts as a neurotransmitter mediating arousal and attention, as well as a pro-inflammatory signal released from mast cells in response to allergic reactions or tissue...
histamine is an important modulator of numerous physiologic processes, including neurotransmission
Neurotransmission
Neurotransmission , also called synaptic transmission, is the process by which signaling molecules called neurotransmitters are released by a neuron , and bind to and activate the receptors of another neuron...
, gastric acid secretion, and smooth muscle tone. The biosynthesis of histamine from histidine is catalyzed by the enzyme L-histidine decarboxylase. This homodimeric enzyme is a pyridoxal phosphate (PLP)-dependent decarboxylase and is highly specific for its histidine substrate.
Some mutations in the gene for this enzyme can cause symptoms of Tourette syndrome
Tourette syndrome
Tourette syndrome is an inherited neuropsychiatric disorder with onset in childhood, characterized by multiple physical tics and at least one vocal tic; these tics characteristically wax and wane...
; however, these mutations have only been observed in one family and are not thought to account for most cases of Tourette syndrome.
In bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
, it is synthesised as a proenzyme, PI. Cleavage
Cleavage
Cleavage may refer to:*Cleavage , partial exposure of the separation between a woman's breasts.**Cleavage enhancement, methods of making a person's breast cleavage look more substantial than it really is....
of the proenzyme PI chain yields two subunits, alpha and beta, which arrange as a hexamer
Hexamer
A hexamer is a thing composed out of six sub-units.In microbiology, a hexamer is one of the proteins composing the polyhedral protein shell that encloses the bacterial micro-compartments known as carboxysomes....
, (alpha beta)6, by nonhydrolytic self-catalysis.