Protein Metabolism – Oxidative Degradation of Amino Acids | 300 Level Biochemistry Lecture Notes

BCH 337: PROTEIN METABOLISM LECTURE NOTE


OXIDATIVE DEGRADATION / METABOLISM OF ONE CARBON UNIT OF AMINO ACIDS

The liver is the principal site of amino acid metabolism, but other tissues, such as the kidney, the
small intestine, muscles, and adipose tissue, take part. Generally, the first step in the breakdown
of amino acids is the separation of the amino group from the carbon skeleton, usually by
a transamination reaction. The carbon skeletons resulting from the deaminated amino acids are
used to form either glucose or fats, or they are converted to a metabolic intermediate that can be
oxidized by the citric acid cycle.
Transamination
Transamination is an exchange of functional groups between any amino acid (except lysine, proline, and
threonine) and an α-keto acid. The amino group is usually transferred to the keto carbon atom of α-
ketoglutarate, converting the α-keto acid to glutamate. Transamination reactions are catalyzed by specific
transaminases (also called aminotransferases), which require pyridoxal phosphate as a coenzyme.