Glossary of Terms

Re-printed from: Information Sheet, PKU Handbook, Australasian Society for Inborn Errors of Metabolism, 1996

Amino Acid

A single chemical unit which collectively combine to form proteins.


Aspartame (Additive No. 951, Nutrasweet and Canderal)

Artificial sweeteners made from phenylalanine and should be avoided by people with PKU.



The metabolic process by which substances are broken down, because the body's energy needs are greater than the energy supplied by the food eaten eg. During an illness with fever, inadequate food intake. This includes the breakdowns of body proteins, which can result in phenylalanine being released.



The capacity for the body to do work. It is provided for by foods, from protein, fat and carbohydrate. Food energy is measured as kilojoule or calorie.



A chemical compound which is involved in the conversion of one substance to another, for example, changing phenylalanine to tyrosine.


Essential Amino Acid

An amino acid which cannot be made by the body and therefore must be provided from the proteins in food.



A unit of heredity, which occur in all cells in the body and form the 'blue prints' for all the bodily processes and traits, such as blood group, hair colour etc.



The branch of biology dealing with the process by which traits are passed from parents to children.


Guthrie Test

A blood test done on all newborn Australian bodies, to measure (among other things) phenylalanine levels.



The transfer of traits and characteristics from parents and ancestors to children.


Maternal PKU

The combination of pregnancy and PKU.



The chemical and physical reactions that occur in the body to support growth, maintenance and other bodily functions.


Non Essential Amino Acid

An amino acid that can be made in the body if the enzyme system is working correctly.



An abbreviation for phenylalanine.



An essential amino acid which accumulates in people who have PKU, when they are not being treated with a protein restricted diet. Sometimes abbreviated as 'phe'.


Phenylketonuria (PKU)

This may vary between centres but generally your child will have contact either directly or indirectly with the following health professionals involved in the diagnosis or treatment of PKU - Doctor, Dietician, Nurse, Social Worker, Newborn Screening Biochemist, Laboratory Technician, Psychologist.



Compounds made up of amino acid 'building blocks' that are essential for growth and regulatory functions in the body.


Protein Supplement

A substance which is a necessary part of the management of PKU. It is phenylalanine free and replaces essential nutrients and amino acids which are otherwise deficient in the restricted PKU diet.



Genes by and large occur in pairs. A gene which is faulty (by 'mistake' or mutation), but which does not affect the carrier in the presence of a normal gene is said to be recessive. In recessive disorders, a person is only affected if both genes of a pair carry a mutation.



A non essential amino acid which is made from phenylalanine in a person without PKU. It becomes an essential amino acid in the person with PKU.


Phenylalanine Units

Most Australian clinics use the United States of American system of counting 15 milligrams of phenylalanine in a food as 1 unit.