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 attached to each carbon atom. They are white, water-soluble solids that c ...

, the reduction product of

galactose Galactose (, ''wikt:galacto-, galacto-'' + ''wikt:-ose#Suffix 2, -ose'', ), sometimes abbreviated Gal, is a monosaccharide sugar that is about as sweetness, sweet as glucose, and about 65% as sweet as sucrose. It is an aldohexose and a C-4 epime ...

. It has a slightly sweet taste. In people with

galactokinase deficiency Galactokinase deficiency is an autosome, autosomal dominance (genetics), recessive inborn errors of metabolism, metabolic disorder marked by an accumulation of galactose and galactitol secondary to the decreased conversion of galactose to galactos ...

, a form of

galactosemia Galactosemia (British galactosaemia, from Greek γαλακτόζη + αίμα, meaning galactose + blood, accumulation of galactose in blood) is a rare genetics, genetic Metabolism, metabolic Disease, disorder that affects an individual's ability t ...

, excess dulcitol forms in the

lens A lens is a transmissive optical device that 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 (anatomy), lens of the eye that leads to a visual impairment, decrease in vision of the eye. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colours, blurry or ...

s. Galactitol is produced from

in a reaction catalyzed by

aldose reductase In enzymology, aldose reductase (or aldehyde reductase) () is an enzyme in humans encoded by the gene AKR1B1. It is an cytosolic NADPH-dependent oxidoreductase that catalyzes the reduction of a variety of aldehydes and carbonyls, including monos ...

. The other common galactose metabolism defect is a defect in

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

, an

autosomal recessive disorder In genetics, dominance is the phenomenon of one variant (allele) of a gene on a chromosome masking or overriding the effect of a different variant of the same gene on the other copy of the chromosome. The first variant is termed dominant and ...

, 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