QDPR
Encyclopedia
QDPR is a human
gene
that produces the enzyme quinoid dihydropteridine reductase. This enzyme is part of the pathway that recycles a substance called tetrahydrobiopterin
, also known as BH4. Tetrahydrobiopterin works with an enzyme called phenylalanine hydroxylase
to process a substance called phenylalanine
. Phenylalanine is an amino acid
(a building block of proteins) that is obtained through the diet; it is found in all protein
s and in some artificial sweeteners. When tetrahydrobiopterin interacts with phenylalanine hydroxylase, tetrahydrobiopterin is altered and must be recycled to a usable form. The regeneration of this substance is critical for the proper processing of several other amino acids in the body. Tetrahydrobiopterin also helps produce certain chemicals in the brain called neurotransmitter
s, which transmit signals between nerve cells.
The QDPR gene is located on the short (p) arm of chromosome 4
at position 15.31, from base pair
17,164,291 to base pair 17,189,981.
In melanocytic cells QDPR gene expression may be regulated by MITF
.
. More than 30 disorder-causing mutations in this gene have been identified, including aberrant splicing, amino acid substitutions, insertions, or premature terminations. These mutations completely, or almost completely, inactivate quinoid dihydropteridine reductase, which prevents the normal recycling of tetrahydrobiopterin. In the absence of usable tetrahydrobiopterin, the body cannot process phenylalanine correctly. As a result, phenylalanine from the diet builds up in the bloodstream and other tissues and can lead to brain damage. Neurotransmitters in the brain are also affected, resulting in delayed development, seizures, movement disorders, and other symptoms.
In addition, a reduction in the activity of quinoid dihydropteridine reductase may cause calcium
to build up abnormally in certain parts of the brain, resulting in damage to nerve cells.
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 the enzyme quinoid dihydropteridine reductase. This enzyme is part of the pathway that recycles a substance called tetrahydrobiopterin
Tetrahydrobiopterin
Tetrahydrobiopterin or sapropterin is a naturally occurring essential cofactor of the three aromatic amino acid hydroxylase enzymes, used in the degradation of amino acid phenylalanine and in the biosynthesis of the neurotransmitters serotonin , melatonin, dopamine, norepinephrine ,...
, also known as BH4. Tetrahydrobiopterin works with an enzyme called phenylalanine hydroxylase
Phenylalanine hydroxylase
Phenylalanine hydroxylase is an enzyme that catalyzes the hydroxylation of the aromatic side-chain of phenylalanine to generate tyrosine. PheOH is one of three members of the pterin-dependent amino acid hydroxylases, a class of monooxygenase that uses tetrahydrobiopterin and a non-heme iron for...
to process a substance called phenylalanine
Phenylalanine
Phenylalanine is an α-amino acid with the formula C6H5CH2CHCOOH. This essential amino acid is classified as nonpolar because of the hydrophobic nature of the benzyl side chain. L-Phenylalanine is an electrically neutral amino acid, one of the twenty common amino acids used to biochemically form...
. Phenylalanine is an 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...
(a building block of proteins) that is obtained through the diet; it is found in all 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...
s and in some artificial sweeteners. When tetrahydrobiopterin interacts with phenylalanine hydroxylase, tetrahydrobiopterin is altered and must be recycled to a usable form. The regeneration of this substance is critical for the proper processing of several other amino acids in the body. Tetrahydrobiopterin also helps produce certain chemicals in the brain called neurotransmitter
Neurotransmitter
Neurotransmitters are endogenous chemicals that transmit signals from a neuron to a target cell across a synapse. Neurotransmitters are packaged into synaptic vesicles clustered beneath the membrane on the presynaptic side of a synapse, and are released into the synaptic cleft, where they bind to...
s, which transmit signals between nerve cells.
The QDPR gene is located on the short (p) arm of chromosome 4
Chromosome 4 (human)
125px|rightChromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 186 million base pairs and represents between 6 and 6.5 percent of the total DNA in cells.Identifying genes on each chromosome is an active area...
at position 15.31, 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...
17,164,291 to base pair 17,189,981.
In melanocytic cells QDPR gene expression may be regulated by MITF
Microphthalmia-associated transcription factor
Microphthalmia-associated transcription factor is a basic helix-loop-helix leucine zipper transcription factor involved in melanocyte and osteoclast development.-Clinical significance:...
.
Related conditions
Mutations in the QDPR gene are a common cause of tetrahydrobiopterin deficiencyTetrahydrobiopterin deficiency
Tetrahydrobiopterin deficiency , also called THB or BH4 deficiency, is a rare metabolic disorder that increases the blood levels of phenylalanine. Phenylalanine is an amino acid obtained through the diet. It is found in all proteins and in some artificial sweeteners...
. More than 30 disorder-causing mutations in this gene have been identified, including aberrant splicing, amino acid substitutions, insertions, or premature terminations. These mutations completely, or almost completely, inactivate quinoid dihydropteridine reductase, which prevents the normal recycling of tetrahydrobiopterin. In the absence of usable tetrahydrobiopterin, the body cannot process phenylalanine correctly. As a result, phenylalanine from the diet builds up in the bloodstream and other tissues and can lead to brain damage. Neurotransmitters in the brain are also affected, resulting in delayed development, seizures, movement disorders, and other symptoms.
In addition, a reduction in the activity of quinoid dihydropteridine reductase may cause calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
to build up abnormally in certain parts of the brain, resulting in damage to nerve cells.