Enzymes called decarboxylases catalyze the removal of the (COOH) from an amino acid. The carboxyl group is an organic functional group consisting of a carbon atom double bonded to an oxygen atom and single bonded to a hydroxyl group. Another way to view it is as a carbonyl group (C=O) that has a hydroxyl group (O-H) attached to the carbon atom.
The carboxyl group is commonly written as -C(=O)OH or -COOH.