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Related Concept Videos

Inborn Errors of Metabolism01:20

Inborn Errors of Metabolism

Phenylketonuria (PKU) is a protein metabolism disorder characterized by high blood levels of the amino acid phenylalanine. This results from a mutation in the gene responsible for phenylalanine hydroxylase, an enzyme that converts phenylalanine into tyrosine. When this enzyme is deficient, phenylalanine builds up in the blood, leading to symptoms such as vomiting, rashes, seizures, growth deficiency, and severe mental retardation. An early diagnosis and a diet restricting phenylalanine intake...
Amino Acid Biosynthetic Pathways01:29

Amino Acid Biosynthetic Pathways

Amino acid biosynthesis is essential for cell growth, protein synthesis, and metabolic regulation. Cells generate essential and non-essential amino acids from metabolic intermediates to sustain vital biological functions. These intermediates originate from key metabolic pathways: glycolysis, the tricarboxylic acid (TCA) cycle, and the pentose phosphate pathway. Important precursors include α-ketoglutarate, pyruvate, oxaloacetate, phosphoenolpyruvate, and erythrose-4-phosphate, which provide...
Overview of Protein Metabolism01:21

Overview of Protein Metabolism

Proteins are broken down into amino acids during digestion. Unlike fats and carbohydrates, which are stored for later use, proteins are not. Instead, amino acids are either used to produce ATP through oxidation or contribute to the creation of new proteins for the growth and repair of the body. Any surplus amino acids from the diet are converted into glucose or triglycerides rather than excreted.
Amino acids play various roles in the body once they are absorbed into cells. They are restructured...
Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase01:27

Pharmacogenetics of Phase II Enzymes: N-acetyltransferase, Thiopurine S-methyltransferase, UDP-glucuronosyltransferase

Phase II biotransformation reactions are essential for detoxifying and eliminating xenobiotics, including many pharmaceutical compounds. These reactions typically involve conjugation, the covalent attachment of polar endogenous groups such as glucuronic acid, sulfate, methyl, or acetyl moieties to functional groups introduced during Phase I metabolism. The resulting conjugates are more water-soluble, enabling efficient renal or biliary excretion.The major classes of Phase II enzymes include...
Pharmacokinetics in Pediatric Patients: Drug Metabolism01:24

Pharmacokinetics in Pediatric Patients: Drug Metabolism

In pediatric care, understanding the nuances of hepatic drug metabolism is crucial, as it significantly differs from that of adults. This divergence is primarily due to the developmental stage of drug-metabolizing enzymes, which affects how medications are processed in the body. In neonates, for instance, the activity of Phase I enzymes—critical for the initial breakdown of drugs—is markedly reduced, functioning at just 20–40% of the levels seen in adults. This reduction poses a challenge in...
Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase01:11

Pharmacogenetics of Drug Targets: β₂-Adrenergic Receptors, Apo E, Thymidylate Synthase

Genetic polymorphisms in drug targets have emerged as critical determinants of interindividual variability in drug response and toxicity. Pharmacogenomic investigations increasingly focus on identifying these variations to personalize and optimize therapeutic interventions. A drug target may be a receptor, enzyme, or signaling protein involved in pharmacologic responses or disease-related pathways. While early pharmacogenetic studies focused primarily on drug metabolism, current research...

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Tyrosine supplementation for phenylketonuria.

Diana Webster1, Joanne Wildgoose

  • 1Nutrition and Dietetic Department, Bristol Royal Hospital for Children, Upper Maudlin Street, Bristol, UK, BS2 8BJ.

The Cochrane Database of Systematic Reviews
|August 6, 2010
PubMed
Summary

Phenylketonuria (PKU) treatment involves a strict diet. While tyrosine supplementation increased blood tyrosine levels in PKU patients, it did not significantly improve other health outcomes. More research is needed to determine its clinical use.

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Area of Science:

  • Metabolic Disorders
  • Nutritional Science
  • Clinical Trials

Background:

  • Phenylketonuria (PKU) is an inherited metabolic disorder requiring strict phenylalanine restriction.
  • The PKU diet is challenging and may lead to tyrosine deficiency, potentially causing neuropsychological issues.
  • Tyrosine supplementation is explored as an adjunct therapy for PKU.

Purpose of the Study:

  • To evaluate the efficacy of tyrosine supplementation in individuals with PKU.
  • To assess its impact on intelligence, neuropsychological performance, growth, nutritional status, mortality, and quality of life.
  • To determine benefits when used with or instead of a phenylalanine-restricted diet.

Main Methods:

  • Systematic review of randomized and quasi-randomized controlled trials.
  • Searched major databases and contacted manufacturers for relevant studies up to June 2010.
  • Included participants with PKU on a phenylalanine-restricted diet, excluding maternal PKU cases.

Main Results:

  • Three trials with 56 participants were included.
  • Tyrosine supplementation significantly increased blood tyrosine concentrations compared to placebo.
  • No significant differences were observed in other measured outcomes like intelligence or growth.

Conclusions:

  • Current evidence is insufficient to recommend routine tyrosine supplementation for PKU.
  • Further high-quality randomized controlled trials are necessary to establish its clinical utility.
  • The role of tyrosine supplementation in PKU management remains uncertain.