Dehydroascorbic Acid - Structure and Physiology

Structure and Physiology

Although there exists a sodium-dependent transporter for vitamin C, it is mainly present in specialized cells, whereas the glucose transporters, most notably GLUT1, transport Vitamin C (in its oxidized form, DHA) in most cells, where recycling back to ascorbate generates the necessary enzyme cofactor and intracellular antioxidant, (see Transport to mitochondria).

The structure shown here for DHA is the commonly shown textbook structure. This 1,2,3-tricarbonyl is too electrophilic to survive more than a few milliseconds in aqueous solution, however. The actual structure shown by spectroscopic studies is the result of rapid hemiacetal formation between the 6-OH and the 3-carbonyl groups. Hydration of the 2-carbonyl is also observed. The lifetime of the stabilized species is commonly said to be about 6 minutes under biological conditions. Destruction results from irreversible hydrolysis of the ester bond, with additional degradation reactions following. Crystallization of solutions of DHA gives a pentacyclic dimer structure of indefinite stability. Recycling of ascorbate via active transport of DHA into cells, followed by reduction and reuse, mitigates the inability of humans to synthesize it from glucose.

Read more about this topic:  Dehydroascorbic Acid

Famous quotes containing the words structure and, structure and/or physiology:

    One theme links together these new proposals for family policy—the idea that the family is exceedingly durable. Changes in structure and function and individual roles are not to be confused with the collapse of the family. Families remain more important in the lives of children than other institutions. Family ties are stronger and more vital than many of us imagine in the perennial atmosphere of crisis surrounding the subject.
    Joseph Featherstone (20th century)

    A committee is organic rather than mechanical in its nature: it is not a structure but a plant. It takes root and grows, it flowers, wilts, and dies, scattering the seed from which other committees will bloom in their turn.
    C. Northcote Parkinson (1909–1993)

    I have more in common with a Mexican man than with a white woman.... This opinion ... chagrins women who sincerely believe our female physiology unequivocally binds all women throughout the world, despite the compounded social prejudices that daily affect us all in different ways. Although women everywhere experience life differently from men everywhere, white women are members of a race that has proclaimed itself globally superior for hundreds of years.
    Ana Castillo (b. 1953)