People with Alkaptonuria Are Usually Placed on Diets Limited in Tyrosine

People with alkaptonuria are usually placed on diets limited in tyrosine because

A) they lack the enzyme that breaks down tyrosine.
B) they lack the enzyme that breaks down a by-product of tyrosine metabolism.
C) due to a difference in one of their enzymes, they produce too much tyrosine.
D) tyrosine alters their enzymes, causing them not to be able to break down homogentisic acid.
E) tyrosine alters their enzymes, causing them to produce too little homogentisic acid.