Brent Cornell

    
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

    
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