Galactolysis refers to the catabolism of galactose.
In the liver, galactose is converted through the Leloir pathway to glucose 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 ^ / \___________/ epimeraseMutations 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 | 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. These are treatable by restricting galactose from the diet. | - | UDPgalactose-4-epimerase deficiency | Is extremely rare (only 2 reported cases). It causes nerve deafness. | - | Galactose-1-phosphate uridyl transferase deficiency | 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. |
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