p-Hydroxyphenylpyruvate Hydroxylase Activity in Fine-Needle Aspiration Liver Biopsies in Hereditary Tyrosinemia

Abstract

The activity of p-hydroxyphenylpyruvate hydroxylase (EC 1.14.2.2) has been determined in fine-needle aspiration biopsies from reference subjects with and without liver disease, patients with hereditary tyrosinemia, and the mother of children with hereditary tyrosinemia. With the assay technique a 0.2 % conversion of substrate to product was clearly detectable. As reference, other enzyme activities were determined in the same homogenate, i.e. aspartate aminotransferase (EC 2.6.1.1), lactate dehydrogenase (EC 1.1.1.27), alanine aminotransferase (EC 2.6.1.2), glycerol-3-phosphate dehydrogenase (EC 1.1.1.8), and sorbitol dehydrogenase (EC 1.1.1. 14). p-Hydroxyphenyl-pyruvate hydroxylase activity could be determined in all reference subjects. There was a considerable interindividual variation, but values obtained from duplicate biopsies on the same patient showed good agreement. In the heterozygote for hereditary tyrosinemia, the p-hydroxyphenylpyruvate hydroxylase activity fell within the range for the reference subjects. In 3 cases of hereditary tyrosinemia enzyme activity corresponding to 1–30 % of the mean value for controls was found. In 2 cases no activity could be demonstrated, but relative to reference enzymes it can be stated that the activity could not have exceeded 1 and 11 %, respectively, of the mean value for reference subjects.

Key Words:

• Amino acid metabolism
• inborn errors
• biopsy
• liver
• enzymes
• hereditary tyrosinemia
• p-hydroxyphenylpyruvate hydroxylase
• tyrosine