Homocystinuria Flashcards
What problems are caused in Homocystinuria?
-High levels of homocysteine affects connective tissue (TF bone, skin, muscle, CNS, CVS etc)
-causes damage to collagen and elastic fibres
^methionine metabolites toxic to neurones
Why is Homocystinuria often mistakenly diagnosed a Marfans syndrome?
Marfans syndrome is a lack of fibrillin-1 protein present in connective tissue
So presents with similar problems- eg lens dislocation, skeletal deformities
What can be caused by faulty/damaged collage and elastin fibres in Homocystinuria?
Lens dislocation
Skeletal deformities
What causes Homocystinuria?
Autosomal recessive
Deficiency in cystathionine B-synthase
What enzyme is deficient in Homocystinuria?
Cystathionine B-synthase
What co-factor does the enzyme deficient in Homocystinuria need?
Active vitamin B6
Cystathionine B-synthase
If the enzyme were not deficient in Homocystinuria, what reaction/conversion would happen?
Methionine–> homocysteine–> cystathionine–> cysteine
In Homocystinuria, what compounds build up? Why does one of them build up?
Homocysteine
Methionine- when high levels of homocysteine, some is converted back to methionine
When there are high levels of homocysteine present, what is it converted to (in Homocystinuria)? What co factor(s) is needed?
Methionine
Vitamin B12
Folate
Betaine
What is homocystine?
Oxidised homocysteine
What is oxidised homocysteine called?
Homocystine
In Homocystinuria, what supplements are needed?
Vit B12, B6
Folate. –to replace those used in converting
Betaine. Homocysteine back to methionine
Cysteine- because with enzyme deficiency none will be produced but we still need a supply of it
Why is cysteine needed by the body?
Used to produce glutathione and hydrogen sulphide
How is Homocystinuria managed?
Low methionine diet
Avoid foods- milk, nuts, cheese, eggs, fish, meat
Supplement diet with Vit B6, B12, Betaine, folate
