Session 3-Galactosaemia Flashcards
What is galactosaemia?
Rare genetic metabolic disorder that affects the individual’s ability to metabolise galactose
Which three enzymes are involved in the initial stages of galactose metabolism?
1) Galactokinase
2) Uridyl transferase
3) UDP-galactose epimerase
What does a galactokinase deficiency lead to an increase in?
Excess of galactose and aldose reductase converts this excess galactose to galactitol
What does a uridyl transferase deficiency lead to an increase in?
Excess of galactose which is converted to galactitol by aldose reductase.
Build up of galactose-1P
What does a UDP-galactose epimerase deficiency lead to an increase in?
Galactotose-1P
What is galactitol?
Sugar alcohol
Why do galactosaemic patients develop cataracts?
Galactokinase or transferase deficiency leads to accumulation of galactose. Aldose reductase converts galactose to galactitol. Increased activity of aldose reductase consumes excess NADPH. This compromises defences against ROS damage. Crystallin protein in lens of eye denatured and this leads to cataracts.
Why do galactosaemic patients become jaundiced?
Uridyl transferase deficiency leads to build up of galactose-1P in the liver which can cause liver damage. One of the functions of the liver is the breakdown of RBCs into bilirubin and liver damage leads to excess of bilirubin, causing jaundice.
How would you treat a patient with galactosaemia?
Put them on a lactose-free diet
Which enzyme deficiency is the most common cause of galactosaemia?
Uridyl transferase
Why does a UDP-galactose epimerase deficiency have serious clinical consequences?
Patient can’t make their own galactose if they don’t have this enzyme and galactose is needed to make glycoproteins
Is there an alternate source of tissue galactose for patients on a galactose free diet?
Yes, they can create galactose from glucose
