Lecture 29: Oxidation of amino acids

Question 1

How is excess nitrogen removed from the body?

Answer 1

Nitrogen in the form of ammonia is toxic in excess and is removed.

• amino groups are transferred to carbon skeletons of for Ala and Glu
• these are transported to the liver where the nitrogen is metabolised into water soluble, non-toxic compound urea
• urea is transported via the blood to the kidneys for excretion in urine

Question 2

What does deamination of amino acids generate ?

Answer 2

a carbon skeleton —> can be used for catabolic/anabolic reactions

a free amino group —> generally excreted

Question 3

Hoe does deamination occur?

- takes place in two ways:

Answer 3

• some amino acids are deaminated by releasing their amino acid groups to solution
  = release of amino group into solution
• some amino acids are deaminated by transferring their amino groups to a keto acid
  = transfer of amino group to a keto acid, which is called transamination

Question 4

What is transamination?

What enzyme catalyses a transamination reaction?

Answer 4

Transfer of an amino group (NH2) to a keto acid (=O) group

• catalysed by transferases which transfer amino groups from a donor amino acid to an acceptor keto acid
• transferases require the coenzyme pyridoxine phosphate which is derived from vitamin B6