The origin of urinary p-hydroxyphenylpyruvate in a patient with hepatic cytosol tyrosine aminotransferase deficiency

Chemical analysis of succinylacetone and 4-hydroxyphenyllactate in amniotic fluid using selective ion monitoring

A method for the measurement of the concentration of succinylacetone and 4-hydroxyphenyllactic acid in amniotic fluid was developed for the prenatal diagnosis of hereditary tyrosinemia. Succinylacetone was converted to 5-methyl-3-isoxazolepropionic acid and isolated with 4-hydroxyphenyllactic acid by liquid partition chromatography and the trimethylsilyl derivatives quantified by ammonia chemical ionization selected ion monitoring gas chromatography-mass spectrometry with 2-hydroxy-n-caproic acid as the internal standard. The concentration of 4-hydroxyphenyllactic acid in normal amniotic fluid was 1.97 +/- 0.75 (S.D.) mumol/l while succinylacetone was undetectable. A pregnancy at risk for tyrosinemia type II was monitored. The concentration of 4-hydroxyphenyllactic acid was within the normal range and a healthy child was born.

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.

A liver urocanase deficiency

Two sisters with a rare inborn error of histidine metabolism resulting from urocanase deficiency are being presented. The more common form of familial histidinemia due to histidase deficiency is excluded. The urocanase deficiency is proven by demonstrating increased excretion of metabolites of the product of the urocanase enzyme action. Further, the strongest evidence for the urocanase defect rests on the demonstration of urocanase deficiency and normal histidase activity in liver.