Galactolysis refers to the catabolism of galactose.
In the liver, galactose is converted through the Leloir pathwaytoglucose 6-phosphate[1] in the following reactions:
galacto- uridyl phosphogluco-
kinase transferase mutase
gal --------> gal 1 P ------------------> glc 1 P -----------> glc 6 P
^ \
/ v
UDP-glc UDP-gal
^ /
\___________/
epimerase
Mutations in the enzymes involved in galactolysis result in metabolic disorders.[2]
There are 3 types of galactosemia or galactose deficiencies:
| Name | Enzyme | Description |
| galactokinase deficiency | Galactokinase | Causes cataracts, which form due to the elevation of galactitol that accumulates when galactose is metabolized in an alternative pathway that is not the Leloir pathway.[2] These are treatable by restricting galactose from the diet. |
| UDPgalactose-4-epimerase deficiency | UDPgalactose-4-epimerase | Is extremely rare (only 2 reported cases). It causes nerve deafness. |
| Galactose-1-phosphate uridyl transferase deficiency | Galactose-1-phosphate uridyl transferase | Is the most problematic, as galactose-free diets are not effective in treating neurocognitive deficiencies (in particular language disorders such as verbal dyspraxia) and ovarian failure. If a galactose-free diet is administered, cataracts and acute symptoms such as kidney and liver failure respond immediately. Formation of cataracts is similar to that in galactokinase deficiency.[2] |
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| Energy metabolism |
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| Fructose / Fructolysis |
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| Sorbitol |
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| Galactose / Galactolysis |
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| Lactose |
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| Mannose |
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