CPSI: Ammonia (High), Citrulline (Low), Urea (Low); OTC: Ammonia (High), Citrulline (Low), Urea (Low); Argininosuccinate Synthetase: Ammonia (High), Citrulline (High), Urea (Low); Orotic Acid: Ammonia (Normal), Citrulline (Normal), Urea (Normal).
In individuals with defects in the urea cycle enzymes, the biochemical profile reflects alterations in ammonia and related metabolites. A deficiency in Carbamoyl Phosphate Synthetase I (CPSI) or Ornithine Transcarbamylase (OTC) results in an accumulation of ammonia, leading to hyperammonemia. This is accompanied by reduced levels of Citrulline and Urea due to the impaired conversion of ammonia into urea. Similarly, a deficiency in Argininosuccinate Synthetase leads to elevated ammonia levels and a decrease in Urea, while Citrulline concentrations may be elevated as it becomes the accumulating intermediate.
On the other hand, defects in the urea cycle do not directly impact Orotic Acid levels; thus, Ammonia, Citrulline, and Urea concentrations remain within normal ranges in this context. Monitoring these metabolites aids in diagnosing and managing urea cycle disorders, highlighting the intricate interplay of enzymes in ammonia detoxification and urea synthesis.