decarboxylases

Decarboxylases are enzymes that catalyze decarboxylation reactions, removing a carboxyl group as carbon dioxide from their substrates. The best-known decarboxylases act on amino acids to produce amines, but many decarboxylases also act on non-amino-acid substrates such as pyruvate or oxaloacetate, contributing to energy metabolism, fermentation, and biosynthesis of specialized compounds.

Most decarboxylases are cofactors-dependent. The majority of amino acid decarboxylases are pyridoxal phosphate (PLP)-dependent, using PLP to stabilize reaction intermediates during decarboxylation. A subset is pyruvoyl-dependent, generated by autocatalytic cleavage of a proenzyme (for example aspartate decarboxylase PanD). Some decarboxylases use other cofactors or function without a classic cofactor, depending on the substrate and organism.

Biological roles are diverse. In animals and humans, decarboxylation reactions produce biogenic amines and neurotransmitters, such as glutamate to GABA (glutamate decarboxylase) and histidine to histamine (histidine decarboxylase). Aromatic L-amino acid decarboxylases, including DOPA decarboxylase (AADC), convert L-DOPA to dopamine and 5-hydroxytryptophan to serotonin. In metabolism and fermentation, ornithine decarboxylase yields putrescine for polyamine synthesis, and pyruvate decarboxylase converts pyruvate to acetaldehyde and CO2 in yeast and some bacteria, influencing flavor and aroma.

Decarboxylases are widespread across bacteria, fungi, plants, and animals, with varied cellular localization and regulation. They have clinical relevance, as modulation of decarboxylase activity can alter neurotransmitter levels, and inhibitors such as carbidopa are used to treat Parkinson’s disease. The enzyme class is also exploited in industrial biotechnology to produce amines and aroma compounds.