Alkaptonuria is a very rare inherited disorder that prevents the body fully breaking down two protein building blocks (amino acids) called tyrosine and phenylalanine. It results in a build-up of a chemical called homogentisic acid in the body.
Alkaptonuria is caused by deficiency of homogentisate 1,2-dioxygenase, an enzyme that converts homogentisic acid (HGA) to maleylacetoacetic acid in the tyrosine degradation pathway. A mutation causing alkaptonuria in the mouse has mapped to chromosome 16.
As shown in the image you can see where that transformation cycle that includes proteins and amino acids breaks down and produces that mutation, which leads to understanding why it occurs in the form of a diagram.
