66 



The Chemistry of the Injured Cell 



the dehalogenase that removes iodine from iodotyrosine or in the 

 enzyme that couples iodotyrosine molecules to form thyroxin. 



In the adrenal gland genetically determined absence of an 

 enzyme involved in the biosynthesis of hydrocortisone may lead to 

 virilism or hypertension due to a secondary overproduction of 

 pituitary corticotropin. The failure may be in the hydroxylation of 

 the steroid ring at the 21 or 1 1 carbon atom. 



Galactose 



Galactose-' 



Phosphate 

 UDP Glucose 



r 



^Glucose-VPhosphate 

 UDP Galactose 



i 



UDP Glucose 



Fig. 9. The Mechanism of Galactosaemia. 



C. Carbohydrate Metabolism 



One example of a genetic abnormality in carbohydrate metabol- 

 ism is galactosaemia. In this condition children are born with an 

 inability to metabolise galactose (a constituent of lactose or milk 

 sugar) which is in consequence excreted in large amounts. The 

 abnormality is due to an inborn absence of the enzyme that couples 



