To use amino acids for energy, the nitrogen must first be removed from the amino acid. this process is called

This process is called deamination.

Deamination is the process (reaction) in which an amine group is removed from a molecule of amino acid. The enzymes that are involved in this reaction are called deaminases. Deamination can be used for energy(break down of amino acids), when there is too much protein intake. Amine group is converted to ammonia that is then converted to urea or uric acid in the urea cycle and at the end excreted through the urine.

In the human body, deamination occurs mostly in the liver (e.g. urea cycle), but also in the kidneys (deamination of glutamate).