Decarboxylases are a group of diverse enzymes that catalyze the decarboxylation of amino acids, keto acids, and others. They have been described in bacteria, plants, and animals.1,2 Although some of their functions remain unknown, it is clear that several of the decarboxylases have biosynthetic functions; e.g., ornithine and adenosylmethionine decarboxylases are required for the synthesis of polyamines,3 and aspartic acid β-decarboxylase and diaminopimelic acid decarboxylase provide one of the biosynthetic routes to alanine and lysine, respectively, in bacteria. Other functions that have been determined for decarboxylases are as follows. First, they are involved in the production of energy; e.g., glycine decarboxylase is involved in the overall conversion of glycine to acetate.4,5 Second, histidine decarboxylase appears to be involved in several physiological processes, e.g., gastric secretion, peripheral circulation, allergic reactions, and certain types of rapid growth.6–8 Third, glutamate decarboxylase (GAD)9,10 and dihydroxyphenylalanine (DOPA) decarboxylase are of primary importance in the nervous system because GAD is the rate-limiting enzyme for the biosynthesis of γ-aminobutyric acid (GABA), an important inhibitory neurotransmitter, and DOPA decarboxylase is involved in the biosynthesis of several neurotransmitters, e.g., serotonin, dopamine, epinephrine, and norepinephrine.10,11