ATP and other purine nucleotides stimulate the inactivation of ornithine transcarbamylase by broken lysosomes.

Ornithine transcarbamylase (OTC) is very stable in rat liver homogenates, or mitochondria. However, pure OTC from rat or beef liver is inactivated by broken lysosomes. ATP and a number of purine nucleotides, particularly epsilon-ATP, stimulate the inactivation of OTC by broken lysosomes. Inactivation of OTC by trypsin and elastase is also stimulated by epsilon-ATP. Carbamoyl phosphate protects OTC against proteolytic attack by elastase or by broken lysosomes. Thus, environmental factors, e.g., ATP and carbamoyl phosphate, appear to influence OTC stability to proteases.