Purity >90%. L-Arginine serves as a common substrate for both nitric oxide synthase (NOS) and arginase in the cell. NOS catalyzes the oxidation of arginine to citrulline and NO with N? -hydroxy-L-arginine formed as an intermediate. Arginase, on the other hand, catalyzes the hydrolysis of arginine into urea and L-ornithine. ABH is a slow-binding competitive inhibitor of human arginase II with Ki values of 0.25 μM and 8.5 nM at pH 7.5 and 9.5, respectively. ABH enhances both male and female sexual arousal responses in rabbits, an effect which may be due to increased NO bioavailability resulting from arginase inhibition. Inhibition of arginase is therefore a potential therapeutic target for the treatment of sexual arousal disorders.