All the more recent work on alkaptonuria has... strengthened the belief that the homogentisic acid excreted is derived from tyrosine, but why alkaptonuric individuals pass the benzene ring of their tyrosine unbroken and how and where the peculiar chemical change from tyrosine to homogentisic acid is brought about, remain unsolved problems.
Archibald E. Garrod
alkaptonuria, belief, biology, problems, science, tyrosine