Structure and properties of the recently discovered aspartate-specific cell death-related plant proteases named phytaspases are reviewed and compared to those of animal apoptotic proteases, caspases. Caspases (cysteine-dependent proteases) and phytaspases (serine-dependent proteases) are structurally very different, yet they share cleavage specificity and a role in programmed cell death. We demonstrate here that the distinctions in structural organization of animal and plant death proteases define differences in the strategies to regulate functioning of these proteolytic enzymes in the two kingdoms.