Exopeptidase that catalyzes the hydrolytic cleavage of multi-L-arginyl-poly-L-aspartic acid (cyanophycin; a water-insoluble reserve polymer) into aspartate-arginine dipeptides. [L-4-(L-arginin-2-N-yl)aspartate](n) + H2O = [L-4-(L-arginin-2-N-yl)aspartate](n-1) + L-4-(L-arginin-2-N-yl)aspartate Inhibited by serine protease inhibitors. Inhibited by N-Bromo-succinimide. Belongs to the peptidase S51 family.