Glutamate decarboxylase (GAD) (GAD)

Glutamate decarboxylase (GAD) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme responsible for the conversion of L-glutamate into gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system. In its role as an antiemetic target, GAD is activated by its essential cofactor, PLP, which is the active metabolite of pyridoxine (vitamin B6). Increased GAD activity leads to elevated GABA levels, which are thought to suppress the vomiting reflex by acting on inhibitory pathways in the chemoreceptor trigger zone (CTZ) and the nucleus tractus solitarius (NTS). This mechanism underlies the clinical use of pyridoxine, often in combination with doxylamine, for the treatment of nausea and vomiting of pregnancy (NVP) and postoperative nausea and vomiting (PONV). Beyond its role in emesis, GAD is a critical enzyme in neurological health, with its dysfunction or autoantibody-mediated inhibition linked to disorders such as epilepsy and stiff-person syndrome. The therapeutic efficacy of pyridoxine as an antiemetic is primarily attributed to its ability to restore or enhance GABAergic tone, thereby providing a safe and effective option for managing pregnancy-related and surgical nausea.

Other names

Glutamate decarboxylase 1 (GAD1)Glutamate decarboxylase 2 (GAD2)GAD67GAD65L-glutamate decarboxylasePyridoxine-associated antiemetic target

Cofactor-mediated enzyme activation leading to increased synthesis of gamma-aminobutyric acid (GABA), which acts as an inhibitory neurotransmitter to suppress the vomiting reflex at the chemoreceptor trigger zone (CTZ).