Urea as a selective inhibitor of argininosuccinate lyase

The effect of urea on various ornithine cycle enzymes has been investigated. It was demonstrated that argininosuccinate lyase was the only ornithine cycle enzyme inhibited by urea in a competitive manner. Based on the data presented the possible role of urea in maintaining a physiological range of intracellular and extracellular urea concentration by controlling hepatic ureogenesis was discussed.