OAT (Ornithine Aminotransferase): OAT is a gene that encodes the ornithine aminotransferase enzyme, which plays a crucial role in the urea cycle. This enzyme catalyses the conversion of ornithine to citrulline, assisting the body in detoxifying ammonia. Mutations in OAT can disrupt this process, resulting in hyperammonaemia — a condition characterised by elevated blood ammonia levels that can impact neurological function.