Development of tyrosine aminotransferase and para-hydroxyphenylpyruvate dioxygenase activities in fetal and neonatal human liver.
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.
D015111:4-Hydroxyphenylpyruvate Dioxygenase / Q000378:metabolism*; D000328:Adult; D001835:Body Weight; D005260:Female; D005333:Fetus / Q000201:enzymology; D006801:Humans; D007231:Infant, Newborn; D008099:Liver / Q000201:enzymology*; D010105:Oxygenases / Q000378:metabolism*; D011247:Pregnancy; D014444:Tyrosine Transaminase / Q000378:metabolism*
D010105:Oxygenases; D015111:4-Hydroxyphenylpyruvate Dioxygenase; D014444:Tyrosine Transaminase