Ornithine ketoacid aminotransferase, also known as OKAT or OAT, is an enzyme that plays a crucial role in the metabolism of amino acids in the human body. It belongs to the aminotransferase family of enzymes, which are responsible for catalyzing the transfer of an amino group from one molecule to another.
Specifically, ornithine ketoacid aminotransferase facilitates the conversion of ornithine, a non-protein amino acid, to its ketoacid derivative, known as Δ1-pyrroline-5-carboxylate (P5C). This reaction requires the participation of a coenzyme, pyridoxal 5'-phosphate (PLP), derived from vitamin B6.
The main function of ornithine ketoacid aminotransferase is to participate in the urea cycle, a critical metabolic pathway responsible for the removal of ammonia from the body. This enzyme catalyzes the transfer of the amino group from ornithine to P5C, producing glutamate and pyrroline-5-carboxylate as intermediates. These intermediates are further metabolized to ultimately form urea, which is excreted in urine, and glutamate, which participates in various biochemical processes.
Defects or deficiencies in the ornithine ketoacid aminotransferase gene can lead to a rare inherited disorder called hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Individuals with HHH syndrome have impaired function of this enzyme, resulting in the buildup of ornithine and ammonia in the blood and tissues. This can lead to neurological symptoms, such as intellectual disability, seizures, and liver dysfunction
