Metabolism of phenylalanine in liver diseases

High Correlation between Results of the [1-¹³C]-Phenylalanine Breath Test and Phenylalanine Hydroxylase (EC 1.14.16.1) Activity of the Liver in Rats

“…2). Heberer et al [10]reported that the slope of the logarithm of the plasma phenylalanine concentration-time curve corresponds to the plasma phenylalanine elimination rate. The logarithm of plasma phenylalanine concentration is shown in the inset of figure 2.…”

“…The amount of tyrosine, the product of PAH reaction, was assayed to determine PAH activity as described by Heberer et al [10]. The reaction mixture, containing 10 m M phenylalanine, 60 U/µl catalase, 50 m M PIPES-K buffer (pH 7.0) and the crude enzyme solution (0.3 mg/ml of protein), was preincubated for 20 min at 25°C.…”

“…The concentration of plasma phenylalanine was fluorometrically determined as described by Heberer et al [10], with some modifications. To 0.16 ml of a mixture of 0.375  M succinate-HCl buffer (pH 5.8), 0.56 m M L -leucyl- L -alanine and 0.625 m M ninhydrine, 0.01 ml of plasma sample or phenylalanine standard was added.…”

Evaluation of 13C-Phenylalanine and 13C-Tyrosine Breath Tests for the Measurement of Hepatocyte Functional Capacity in Patients with Liver Cirrhosis.

“…C]phenylalanine or L- [1][2][3][4][5][6][7][8][9][10][11][12][13] C]tyrosine, 100 mg per subject in 100 ml of water. The container was then rinsed with 100 ml of water, which the subjects also drank.…”

Hepatic amino-acid metabolism in liver cirrhosis and in the long-term course after liver transplantation

“…Although diminished plasma clearance of intravenously administered AAAs [14,19,221 and methionine [3] has been noted in patients with advanced cirrhosis, to our knowledge no direct measurement of hepatic AAA and methionine uptake has been reported in patients with liver cirrhosis or after OLT. Our data demonstrate that the increase of AAA and methionine plasma levels in cirrhosis has two components: HSS of these amino acids and hepatic clearance.…”