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January 1967

The Enzymatic Deficiency in Tyrosinemia

Am J Dis Child. 1967;113(1):54-57. doi:10.1001/archpedi.1967.02090160104010

SOME time ago I reviewed the literature on tyrosinosis to write a chapter on this subject.1 This required careful restudy of the classic investigations by Dr. Grace Medes in 1927 of a metabolic disorder of tyrosine metabolism, which she named, tyrosinosis.2,3 In the intervening 30 years since her studies, considerable advances have been made in our understanding of tyrosine metabolism both in vitro and in vivo. With this additional information, the biochemical findings and conclusions were reexamined. It seemed more probable that the enzymatic deficiency underlying the metabolic disorder in her patient was a deficiency of liver tyrosine transaminase (tyrosine-α-ketoglutarate-aminotransferase) rather than a deficiency of p-hydroxyphenylpyruvic acid (pHPPA) oxidase, as had been originally proposed. Two biochemical abnormalities were found which are more compatible with the alternative proposal: the patient excreted 3,4-dihydroxyphenylalanine (dopa) when large amounts of tyrosine were ingested; and he excreted large amounts of pHPPA but

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