sentences:  Holden and coworkers then mimicked that tetrahedral transition state to design a series of phosphonamidate peptide analogues.Among the synthesized analogues, R = L-Leu possesses the most potent inhibitory activity ("K"i = 9.1 nM).Arginase is a binuclear manganese metalloprotein that catalyses the hydrolysis of L-arginine to L-ornithine and urea.