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Comprehensive Biotransformation Analysis of Phenylalanine-Tyrosine Metabolism Reveals Alternative Routes of Metabolite Clearance in Nitisinone-Treated Alkaptonuria

Norman, BP, Davison, AS, Hickton, B, Ross, GA, Milan, AM, Hughes, AT, Wilson, PJM, Sutherland, H, Hughes, JH, Roberts, NB, Bou-Gharios, G, Gallagher, JA and Ranganath, LR (2022) Comprehensive Biotransformation Analysis of Phenylalanine-Tyrosine Metabolism Reveals Alternative Routes of Metabolite Clearance in Nitisinone-Treated Alkaptonuria. Metabolites, 12 (10). ISSN 2218-1989

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Open Access URL: https://doi.org/10.3390/metabo12100927 (Published version)


Metabolomic analyses in alkaptonuria (AKU) have recently revealed alternative pathways in phenylalanine-tyrosine (phe-tyr) metabolism from biotransformation of homogentisic acid (HGA), the active molecule in this disease. The aim of this research was to study the phe-tyr metabolic pathway and whether the metabolites upstream of HGA, increased in nitisinone-treated patients, also undergo phase 1 and 2 biotransformation reactions. Metabolomic analyses were performed on serum and urine from patients partaking in the SONIA 2 phase 3 international randomised-controlled trial of nitisinone in AKU (EudraCT no. 2013-001633-41). Serum and urine samples were taken from the same patients at baseline (pre-nitisinone) then at 24 and 48 months on nitisinone treatment (patients N = 47 serum; 53 urine) or no treatment (patients N = 45 serum; 50 urine). Targeted feature extraction was performed to specifically mine data for the entire complement of theoretically predicted phase 1 and 2 biotransformation products derived from phenylalanine, tyrosine, 4-hydroxyphenylpyruvic acid and 4-hydroxyphenyllactic acid, in addition to phenylalanine-derived metabolites with known increases in phenylketonuria. In total, we observed 13 phase 1 and 2 biotransformation products from phenylalanine through to HGA. Each of these products were observed in urine and two were detected in serum. The derivatives of the metabolites upstream of HGA were markedly increased in urine of nitisinone-treated patients (fold change 1.2–16.2) and increases in 12 of these compounds were directly proportional to the degree of nitisinone-induced hypertyrosinaemia (correlation coefficient with serum tyrosine = 0.2–0.7). Increases in the urinary phenylalanine metabolites were also observed across consecutive visits in the treated group. Nitisinone treatment results in marked increases in a wider network of phe-tyr metabolites than shown before. This network comprises alternative biotransformation products from the major metabolites of this pathway, produced by reactions including hydration (phase 1) and bioconjugation (phase 2) of acetyl, methyl, acetylcysteine, glucuronide, glycine and sulfate groups. We propose that these alternative routes of phe-tyr metabolism, predominantly in urine, minimise tyrosinaemia as well as phenylalanaemia.

Item Type: Article
Uncontrolled Keywords: alkaptonuria; biotransformations; detoxification; hypertyrosinaemia; metabolomics; 0301 Analytical Chemistry; 0601 Biochemistry and Cell Biology; 1103 Clinical Sciences
Subjects: Q Science > QD Chemistry
Q Science > QH Natural history > QH301 Biology
Divisions: Sport & Exercise Sciences
Publisher: MDPI AG
SWORD Depositor: A Symplectic
Date Deposited: 02 Mar 2023 10:28
Last Modified: 02 Mar 2023 10:28
DOI or ID number: 10.3390/metabo12100927
URI: https://researchonline.ljmu.ac.uk/id/eprint/18986
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