Porphobilinogen synthase
Encyclopedia
Porphobilinogen synthase (or ALA dehydratase, or aminolevulinate dehydratase) synthesizes porphobilinogen
through the asymmetric condensation
of two molecules of aminolevulinic acid. All natural tetrapyrroles, including heme
s, chlorophyll
s and vitamin B12
, share porphobilinogen as a common precursor.
It is involved in the second step of the metabolism of porphyrin
.
A deficiency of porphobilinogen synthase is usually acquired (rather than hereditary) and and can be caused by heavy metal poisoning
, especially lead poisoning
, as the enzyme is very susceptible to inhibition by heavy metals.
Hereditary insufficiency of porphobilinogen synthase is called porphobilinogen synthase (or ALA dehydratase) deficiency poprhyria
. It is an extremely rare cause of porphyria
, with less than 10 cases ever reported.
Lead poisoning
works on the cellular level by binding to this enzyme
, rendering it useless.
Porphobilinogen
Porphobilinogen is a pyrrole involved in porphyrin metabolism.It is generated by aminolevulinate and the enzyme ALA dehydratase. PBG is then converted into hydroxymethyl bilane by the enzyme porphobilinogen deaminase, also known as hydroxymethylbilane synthase.Acute intermittent porphyria causes...
through the asymmetric condensation
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....
of two molecules of aminolevulinic acid. All natural tetrapyrroles, including heme
Heme
A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as their prosthetic group; these are...
s, chlorophyll
Chlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
s and vitamin B12
Vitamin B12
Vitamin B12, vitamin B12 or vitamin B-12, also called cobalamin, is a water-soluble vitamin with a key role in the normal functioning of the brain and nervous system, and for the formation of blood. It is one of the eight B vitamins...
, share porphobilinogen as a common precursor.
It is involved in the second step of the metabolism of porphyrin
Porphyrin
Porphyrins are a group of organic compounds, many naturally occurring. One of the best-known porphyrins is heme, the pigment in red blood cells; heme is a cofactor of the protein hemoglobin. Porphyrins are heterocyclic macrocycles composed of four modified pyrrole subunits interconnected at...
.
Deficiency
A deficiency of porphobilinogen synthase is usually acquired (rather than hereditary) and and can be caused by heavy metal poisoning
Heavy Metal Poisoning
Heavy Metal Poisoning is a song by American rock band Styx. It was included as the fifth track on their 1983 studio album Kilroy Was Here.The song in the story of Kilroy Was Here has the character of Dr Righteous preaching the evils of rock and roll...
, especially lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
, as the enzyme is very susceptible to inhibition by heavy metals.
Hereditary insufficiency of porphobilinogen synthase is called porphobilinogen synthase (or ALA dehydratase) deficiency poprhyria
Aminolevulinic acid dehydratase deficiency porphyria
Aminolevulinic acid dehydratase deficiency porphyria is a cutaneous condition, disease can present during early childhood with acute neurologic symptoms that resemble those encountered in acute intermittent porphyria...
. It is an extremely rare cause of porphyria
Porphyria
Porphyrias are a group of inherited or acquired disorders of certain enzymes in the heme bio-synthetic pathway . They are broadly classified as acute porphyrias and cutaneous porphyrias, based on the site of the overproduction and accumulation of the porphyrins...
, with less than 10 cases ever reported.
 |
Lead poisoning
Lead poisoning
Lead poisoning is a medical condition caused by increased levels of the heavy metal lead in the body. Lead interferes with a variety of body processes and is toxic to many organs and tissues including the heart, bones, intestines, kidneys, and reproductive and nervous systems...
works on the cellular level by binding to this enzyme
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...
, rendering it useless.