Tyrosine transaminase activity in normal and cirrhotic liver

Digestive Diseases and Sciences
J M HendersonD Rudman

Abstract

Most cirrhotics have tyrosinemia and subnormal tyrosine tolerance; in some the ability to metabolize p-hydroxyphenylpyruvic and homogentisic acids is impaired. In previous studies, the initial transamination appeared to be the rate-limiting step. In this study, hepatic tyrosine transaminase activity was compared in liver biopsies from eight noncirrhotic and ten cirrhotic subjects to determine whether the subnormal tyrosine tolerance was related to decreased maximal activity of this enzyme. Fasting plasma tyrosine in the cirrhotics (133 +/- 43 micromol/liter) was significantly higher (P less than 0.005) than in the noncirrhotic subjects (64 +/- 25 micromol/liter). Tyrosine transaminase activity in the cirrhotic livers (42 +/- 11 micromol PHPA/g liver/hr, or 0.47 +/- 0.1 micromol PHPA/mg protein/hr) was not significantly different from the enzyme activity in the noncirrhotic liver (43 +/- 7 micromol PHPA/g liver/hr, or 0.39 +/- .12 micromol PHPA/mg protein/hr.) Thus elevated tyrosine levels in cirrhotics cannot be explained by decreased tyrosine transaminase activity in the liver, and other explanations must be sought.

References

Aug 1, 1979·The Journal of Clinical Investigation·B A FarajD Rudman
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Dec 1, 1973·American Journal of Surgery·D P CampbellC E Anagnostopoulos
Dec 1, 1967·The Journal of Clinical Investigation·R J Levine, H O Conn

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Citations

Apr 1, 1993·European Journal of Clinical Chemistry and Clinical Biochemistry : Journal of the Forum of European Clinical Chemistry Societies·D J ByrdJ Brodehl
Jan 19, 2008·Journal of Nutritional Science and Vitaminology·Shigeko Fujimoto SakataNanaya Tamaki
Sep 24, 2005·European Journal of Clinical Investigation·W YanX Sun
Jul 1, 1984·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·P SchauderU Langenbeck
May 1, 1986·Hepatology : Official Journal of the American Association for the Study of Liver Diseases·J M HendersonA H Merrill

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