Abstract
Extract: Metabolic studies on a patient having multiple congenital anomalies and defective hepatic soluble tyrosine aminotransferase activity are presented. The activities of hepatic mitochondrial tyrosine aminotransferase and soluble p-hydroxyphenylpyryvate hydroxylase were normal. When untreated, levels of tyrosine in plasma rose as high as 62 mg/100 ml. He had phenolic aciduri (3.1–4.9 mg/mg creatinine) with p-hydroxyphenylpyruvic acid (0.6-1.8 mg/mg creatinine), p-hydroxyphenylacetic acid (0.7–1.2 mg/mg creatinine), p-hydroxyphenyllactic acid (1.0–1.7 mg/mg creatinine), and N-acetyltyrosine (0.9–1.6 mg/mg creatinine). These metabolites were identified by gas chromatography-mass spectrometry. Excretion of p-tyramine was grossly elevated (17–44 μg/mg creatinine) and was not reduced by orally administered antibiotics. Oral tolerance tests showed rapid conversion of phenylpyruvic acid to phenylalanine and of phenylalanine to tyrosine.
Speculation: The results described suggest the need to reexamine subcellular distribution of enzymes both in normal subkects and in patients with inborn errors of metabolism. When methods are developed to fractionate tyrosine aminotransferase, it may become apparent that there are several isozymes under individual genetic control. Accumulation of an intermediary metabolite should not be taken as conclusive evidence of a primary abnormality of its catabolism. The similarity of the findings in the urine of a patient with hepatic soluble tyrosine aminotransferase deficiency and in tyrosyluric neonates suggests that delayed maturation of soluble tyrosine aminotransferase rather than p-hydroxyphenylpyruvate hydroxylase might be present in at least some of these infants.
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Kennaway, N., Buist, N. Metabolic Studies in a Patient with Hepatic Cytosol Tyrosine Aminotransferase Deficiency. Pediatr Res 5, 287–297 (1971). https://doi.org/10.1203/00006450-197107000-00002
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DOI: https://doi.org/10.1203/00006450-197107000-00002
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