In this study, the inhibition effects of guanidin and some amino acids on arginase activity in sheep liver tissue were studied. Thiosemicarbazide-Diacetylmonoxime-Urea method was used to measure arginase activity.

Guanidin, a guanidino compound, inhibited the enzyme activity uncompetetively while L-amino acids, such as valine, leucine, isoleucine and lysine inhibited the enzyme activity competetively-noncompetetively (mixed). Low concentration of leucine caused activation while higher concentration caused inhibition.