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Dehydroascorbic acid

 

 
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Dehydroascorbic acid
 
 
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Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid
Ascorbic acid

Ascorbic acid is a sugar acid with antioxidant properties. Its appearance is white to light-yellow crystals or powder. It is water-soluble. The L-enantiomer of ascorbic acid is commonly known as vitamin C....
. It is actively imported into the endoplasmic reticulum
Endoplasmic reticulum

The endoplasmic reticulum is a eukaryote organelle that forms an interconnected network of tubules, vesicle , and cisternae within cell . The lacey membranes of the endoplasmic reticulum were first seen by Keith R....
 of cells and generates the oxidative potential found there. Protein disulfide isomerase
Protein disulfide isomerase

Protein disulfide isomerase or PDI is an enzyme in the endoplasmic reticulum in eukaryotes or periplasmic space of prokaryotes that catalyzes the formation and breakage of disulfide bonds between cysteine residues within proteins as they fold....
s are known to reduce DHA back to ascorbic acid, oxidizing their disulfide bonds in the process. Therefore L-dehydroascorbic acid is a vitamin C compound much like L-ascorbic acid. Oxidized forms of esterified ascorbic acids can be numbered at C(5) or C(6) atoms and the (free) chemical radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
 semi-dehydroascorbate or semidehydro ascorbic acid (SDA) to the group of dehydroascorbic acids.

ough there exists a transporter for Vitamin C
Vitamin C

Vitamin C or ascorbic acid is an essential nutrient for humans, a large number of simian species, a small number of other mammalian species , a few species of birds, and some fish....
, it is mainly present in specialized cells, whereas the glucose transporter
Glucose transporter

Glucose transporters are a family of membrane proteins found in most mammals....
s, most notably GLUT1
GLUT1

GLUT1 was the first glucose transporter to be characterized. It is widely distributed in fetal tissues. In the adult it is expressed at highest levels in erythrocytes and also in the endothelial cells of barrier tissues such as the blood-brain barrier....
, ensure in most cells of the body the transport of vitamin C (in its oxidized form, DHA) where it is required as an enzyme cofactor and an intracellular antioxidant, after it is recycled back to ascorbic acid (see Transport to mitochondria).

min C accumulates in mitochondria, where most of the free radicals are produced, by entering through the glucose transporters, GLUT1.






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Encyclopedia


Dehydroascorbic acid (DHA) is an oxidized form of ascorbic acid
Ascorbic acid

Ascorbic acid is a sugar acid with antioxidant properties. Its appearance is white to light-yellow crystals or powder. It is water-soluble. The L-enantiomer of ascorbic acid is commonly known as vitamin C....
. It is actively imported into the endoplasmic reticulum
Endoplasmic reticulum

The endoplasmic reticulum is a eukaryote organelle that forms an interconnected network of tubules, vesicle , and cisternae within cell . The lacey membranes of the endoplasmic reticulum were first seen by Keith R....
 of cells and generates the oxidative potential found there. Protein disulfide isomerase
Protein disulfide isomerase

Protein disulfide isomerase or PDI is an enzyme in the endoplasmic reticulum in eukaryotes or periplasmic space of prokaryotes that catalyzes the formation and breakage of disulfide bonds between cysteine residues within proteins as they fold....
s are known to reduce DHA back to ascorbic acid, oxidizing their disulfide bonds in the process. Therefore L-dehydroascorbic acid is a vitamin C compound much like L-ascorbic acid. Oxidized forms of esterified ascorbic acids can be numbered at C(5) or C(6) atoms and the (free) chemical radical
Radical (chemistry)

In chemistry, radicals are atoms, molecules or ions with unpaired electrons on an otherwise open shell configuration. These unpaired electrons are usually highly chemical reaction, so radicals are likely to take part in chemical reactions....
 semi-dehydroascorbate or semidehydro ascorbic acid (SDA) to the group of dehydroascorbic acids.

Physiology


Although there exists a transporter for Vitamin C
Vitamin C

Vitamin C or ascorbic acid is an essential nutrient for humans, a large number of simian species, a small number of other mammalian species , a few species of birds, and some fish....
, it is mainly present in specialized cells, whereas the glucose transporter
Glucose transporter

Glucose transporters are a family of membrane proteins found in most mammals....
s, most notably GLUT1
GLUT1

GLUT1 was the first glucose transporter to be characterized. It is widely distributed in fetal tissues. In the adult it is expressed at highest levels in erythrocytes and also in the endothelial cells of barrier tissues such as the blood-brain barrier....
, ensure in most cells of the body the transport of vitamin C (in its oxidized form, DHA) where it is required as an enzyme cofactor and an intracellular antioxidant, after it is recycled back to ascorbic acid (see Transport to mitochondria).

Transport to mitochondria

Vitamin C accumulates in mitochondria, where most of the free radicals are produced, by entering through the glucose transporters, GLUT1. It is the oxidized form (dehydroascorbic acid) that is transported by GLUT1, not the reduced form (ascorbic acid). Ascorbic acid protects the mitochondrial genome
Mitochondrial genome

The mitochondrial genome is the genetic material of the mitochondria. The mitochondria are organelles that reproduce themselves semi-autonomously within eukaryote cells....
 and membrane.

Transport to the brain

Vitamin C does not pass from the blood stream into the brain
Brain

The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as cnidarian and echinoderm have a decentralized nervous system without a brain, while sponges lack any nervous system at all....
, although the brain is one of the organs which has the greatest concentration of vitamin C. Instead it is dehydroascorbate that is transported through the blood-brain barrier
Blood-brain barrier

The blood-brain barrier is a metabolic or cellular structure in the central nervous system that restricts the passage of various chemical substances and microscopic objects between the bloodstream and the neural tissue itself, while still allowing the passage of substances essential to metabolism function ....
 via GLUT1 transporters
GLUT1

GLUT1 was the first glucose transporter to be characterized. It is widely distributed in fetal tissues. In the adult it is expressed at highest levels in erythrocytes and also in the endothelial cells of barrier tissues such as the blood-brain barrier....
, and then converted to vitamin C. Some research has suggested that administration of dehydroascorbic acid may confer protection from neuronal injury following an ischemic stroke.

Further reading