decarboxylase

Decarboxylases are enzymes that catalyze decarboxylation, the removal of a carboxyl group as carbon dioxide, from a variety of substrates. They are found in bacteria, plants, and animals and play important roles in metabolism and signaling. Many decarboxylases require pyridoxal phosphate (PLP) as a cofactor, which facilitates the transfer of the amino group and the release of CO2; some operate with different prosthetic groups, such as a pyruvoyl moiety in certain proenzymes.

Common examples include amino acid decarboxylases, such as glutamate decarboxylase (GAD), which converts glutamate to gamma-aminobutyric acid (GABA); histidine decarboxylase, producing histamine; tyrosine decarboxylase, forming tyramine and related amines; and tryptophan decarboxylase, contributing to serotonin biosynthesis. Non-amino-acid decarboxylases include enzymes like pyruvate decarboxylase, which converts pyruvate to acetaldehyde, and oxaloacetate decarboxylase, involved in metabolic pathways. In many enzyme classification schemes, decarboxylases are grouped under EC 4.1.1.x, the carboxy-lyases that remove carbon dioxide.

Functionally, decarboxylation influences neurotransmitter pools, amino acid metabolism, and pH regulation. In bacteria, decarboxylases can enhance acid resistance by consuming protons during amino acid decarboxylation. In medicine, decarboxylase inhibitors such as carbidopa are used to modulate neurotransmitter synthesis, for example in Parkinson’s disease to improve peripheral levodopa availability. Genetic and regulatory changes affecting decarboxylases can therefore impact physiological signaling and metabolic flux.