PPOX
Encyclopedia
Protoporphyrinogen oxidase is an enzyme
that in humans is encoded by the PPOX gene
.
PPOX (protoporphyrinogen oxidase) is a human
gene
that produces an enzyme
called protoporphyrinogen oxidase
. This enzyme is responsible for the seventh step in heme
production. Heme is the portion of hemoglobin that carries oxygen in the blood from the lungs to the rest of the body. Each of the steps in heme production is controlled by a separate gene (see below). Protoporphyrinogen oxidase removes hydrogen
atoms from protoporphyrinogen IX
(the product of the sixth step in the production of heme) to form protoporphyrin IX
. One additional enzyme must modify protoporphyrin IX before it becomes heme
.
The PPOX gene is located on the long (q) arm of chromosome 1
at position 22, from base pair
157,949,266 to base pair 157,954,082.
The following genes are part of the chemical pathway for making heme.
is caused by mutations in the PPOX gene. More than 100 mutations that can cause variegate porphyria have been identified in the PPOX gene. One mutation, a substitution of the amino acid
tryptophan
for arginine
at position 59 (also written as Arg59Trp or R59W), is found in about 95 percent of South African families with variegate porphyria. Mutations in the PPOX gene reduce the activity of the enzyme made by the gene, allowing byproducts of heme production to build up in the body. This buildup, in combination with nongenetic factors (such as certain drugs, alcohol
and dieting), causes this type of porphyria.
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 in humans is encoded by the PPOX 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...
.
PPOX (protoporphyrinogen oxidase) is a human
Human
Humans are the only living species in the Homo genus...
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...
that produces an 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...
called protoporphyrinogen oxidase
Protoporphyrinogen oxidase
Protoporphyrinogen oxidase is an enzyme that is responsible for the seventh step in heme production....
. This enzyme is responsible for the seventh step in 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...
production. Heme is the portion of hemoglobin that carries oxygen in the blood from the lungs to the rest of the body. Each of the steps in heme production is controlled by a separate gene (see below). Protoporphyrinogen oxidase removes hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
atoms from protoporphyrinogen IX
Protoporphyrinogen IX
Protoporphyrinogen IX is a precursor for protoporphyrin IX. See Porphyrins for the pathway and more information.-See also:* Protoporphyrinogen oxidase...
(the product of the sixth step in the production of heme) to form protoporphyrin IX
Protoporphyrin IX
Protoporphyrin IX, in the metabolism of porphyrin, is created by the enzyme protoporphyrinogen oxidase.-Heme b biosynthesis:In heme biosynthesis, the enzyme ferrochelatase converts it into heme b Protoporphyrin IX, in the metabolism of porphyrin, is created by the enzyme protoporphyrinogen...
. One additional enzyme must modify protoporphyrin IX before it becomes 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...
.
The PPOX gene is located on the long (q) arm of chromosome 1
Chromosome 1 (human)
Chromosome 1 is the designation for the largest human chromosome. Humans have two copies of chromosome 1, as they do with all of the autosomes, which are the non-sex chromosomes. Chromosome 1 spans about 247 million nucleotide base pairs, which are the basic units of information for DNA...
at position 22, from base pair
Base pair
In molecular biology and genetics, the linking between two nitrogenous bases on opposite complementary DNA or certain types of RNA strands that are connected via hydrogen bonds is called a base pair...
157,949,266 to base pair 157,954,082.
The following genes are part of the chemical pathway for making heme.
- ALADALADDelta-aminolevulinic acid dehydratase is an enzyme that in humans is encoded by the ALAD gene.-Further reading:...
: aminolevulinate, delta-, dehydratase - ALAS1ALAS1Delta-aminolevulinate synthase 1 also known as ALAS1 is a protein that in humans is encoded by the ALAS1 gene. ALAS1 is an aminolevulinic acid synthase....
: aminolevulinate, delta-, synthase 1 - ALAS2ALAS2Delta-aminolevulinate synthase 2 also known as ALAS2 is a protein that in humans is encoded by the ALAS2 gene. ALAS2 is an aminolevulinic acid synthase....
: aminolevulinate, delta-, synthase 2 (sideroblastic/hypochromic anemia) - CPOXCPOXCPOX may refer to:*Coproporphyrinogen III oxidase*Catalytic partial oxidation...
: coproporphyrinogen oxidase - FECH: ferrochelatase (protoporphyria)
- HMBS: hydroxymethylbilane synthase
- PPOX: protoporphyrinogen oxidase
- UROD: uroporphyrinogen decarboxylase
- UROSUrosThe Uros are a pre-Incan people who live on forty-two self-fashioned floating islands in Lake Titicaca Puno, Peru and Bolivia. They form three main groups: Uru-Chipayas, Uru-Muratos and the Uru-Iruitos...
: uroporphyrinogen III synthase (congenital erythropoietic porphyria)
Related conditions
Variegate porphyriaVariegate porphyria
Variegate porphyria is an autosomal dominant porphyria that can have acute symptoms along with symptoms that affect the skin...
is caused by mutations in the PPOX gene. More than 100 mutations that can cause variegate porphyria have been identified in the PPOX gene. One mutation, a substitution of the amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
for arginine
Arginine
Arginine is an α-amino acid. The L-form is one of the 20 most common natural amino acids. At the level of molecular genetics, in the structure of the messenger ribonucleic acid mRNA, CGU, CGC, CGA, CGG, AGA, and AGG, are the triplets of nucleotide bases or codons that codify for arginine during...
at position 59 (also written as Arg59Trp or R59W), is found in about 95 percent of South African families with variegate porphyria. Mutations in the PPOX gene reduce the activity of the enzyme made by the gene, allowing byproducts of heme production to build up in the body. This buildup, in combination with nongenetic factors (such as certain drugs, alcohol
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
and dieting), causes this type of porphyria.