Amino Acids

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•  Some fatty acids and some amino acids are essential

•  Lack of essential amino acids affects the production of proteins

Amino acids are the monomeric building blocks from which proteins are constructed

  • There are 20 different amino acids which are universal to all living organisms

Amino acids can be either essential, non-essential or conditionally non-essential according to dietary requirements

  • Essential amino acids cannot be produced by the body and must be present in the diet
  • Non-essential amino acids can be produced by the body and are therefore not required as part of the diet
  • Conditionally non-essential amino acids can be produced by the body, but at rates lower than certain conditional requirements (e.g. during pregnancy or infancy) – they are essential at certain times only

A shortage of one or more essential amino acids in the diet will prevent the production of specific proteins

  • This is known as protein deficiency malnutrition and the health effects will vary depending on the amino acid shortage

Essential vs Non-Essential Amino Acids

essential amino acids

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•  Cause and treatment of phenylketonuria

Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine

  • It is an autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase
  • Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine
  • In people with PKU, the excess phenylalanine is instead converted into phenylpyruvate (also known as phenylketone)
  • This results in a toxic build up of phenylketone in the blood and urine (hence phenylketonuria)

Untreated PKU can lead to brain damage and mental retardation, as well as other serious medical problems

  • Infants with PKU are normal at birth because the mother is able to break down phenylalanine during pregnancy
  • Diagnosis of PKU is made by a simple blood test for elevated phenylalanine levels shortly after birth

PKU is treated by enforcing a strict diet that restricts the intake of phenylalanine to prevent its build up within the body

  • This low-protein diet should include certain types of fruits, grains, vegetables and special formula milk
  • This diet should be supplemented with a medical formula that contains precise quantities of essential amino acids
  • Patients who are diagnosed early and maintain this strict diet can have a normal life span without damaging symptoms

Metabolism of Phenylalanine – Healthy vs PKU