Galactitol (dulcitol) is a

sugar alcohol Sugar alcohols (also called polyhydric alcohols, polyalcohols, alditols or glycitols) are organic compounds, typically derived from sugars, containing one hydroxyl group (–OH) attached to each carbon atom. They are white, water-soluble solids ...

, the reduction product of

galactose Galactose (, '' galacto-'' + '' -ose'', "milk sugar"), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epimer of glucose. A galactose molec ...

. It has a slightly sweet taste. In people with

galactokinase deficiency Galactokinase deficiency is an autosomal recessive metabolic disorder marked by an accumulation of galactose and galactitol secondary to the decreased conversion of galactose to galactose-1-phosphate by galactokinase. The disorder is caused by mu ...

, a form of

galactosemia Galactosemia (British galactosaemia, from Greek γαλακτόζη + αίμα, meaning galactose + blood, accumulation of galactose in blood) is a rare genetic metabolic disorder that affects an individual's ability to metabolize the sugar galacto ...

, excess dulcitol forms in the

lens A lens is a transmissive optical device which focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements''), ...

of the eye leading to

cataract A cataract is a cloudy area in the lens of the eye that leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry or double vision, halos around light, trouble w ...

s. Galactitol is produced from

in a reaction catalyzed by

aldose reductase In enzymology, aldose reductase (or aldehyde reductase) () is a cytosolic NADPH-dependent oxidoreductase that catalyzes the reduction of a variety of aldehydes and carbonyls, including monosaccharides. It is primarily known for catalyzing the re ...

. The other common galactose metabolism defect is a defect in

galactose-1-phosphate uridylyltransferase Galactose-1-phosphate uridylyltransferase (or GALT, G1PUT) is an enzyme () responsible for converting ingested galactose to glucose. Galactose-1-phosphate uridylyltransferase (GALT) catalyzes the second step of the Leloir pathway of galactose ...

, an

autosomal recessive disorder An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes ...

, which also causes a buildup of galactitol as a result of increased concentrations of galactose-1-phosphate and galactose. This disorder leads to cataracts caused by galactitol buildup.

References

External links

* {{Fructose and galactose metabolic intermediates Sugar alcohols Sugar substitutes