Development of tyrosine aminotransferase and para-hydroxyphenylpyruvate dioxygenase activities in fetal and neonatal human liver.

J J Ohisalo; T Laskowska-Klita; S M Andersson

doi:10.1172/JCI110593

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Published in Volume 70, Issue 1 on July 1, 1982
J Clin Invest. 1982;70(1):198–200. https://doi.org/10.1172/JCI110593.
© 1982 The American Society for Clinical Investigation

Published July 1, 1982 - Version history

In livers of fetuses of 220--340 g body wt, total cytosolic tyrosine aminotransferase activity was 1.0 nmol of product/mg of protein per min, and the corresponding values for autopsy livers of newborns of 740--1,475 g and 2,600--3,650 g were 1.5 and 5.7, respectively, as compared with the adult value of 12.7. On the other hand, para-hydroxyphenylpyruvate dioxygenase activity is at adult level already in fetuses less than 340 g body wt. The Km value for tyrosine of tyrosine aminotransferase (1 mM) was considerably higher than the corresponding value for para-hydroxyphenylpyruvate of para-hydroxyphenylpyruvate dioxygenase (50 micro M). These results suggest that tyrosine aminotransferase is the rate limiting enzyme in the catabolism of tyrosine in premature infants.

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