Abstract
We have shown that vacuolar processing enzyme (VPE) exhibits caspase-1 activity in virus-induced hypersensitive cell death (1). Caspase-1 is a cysteine proteinase and an executioner in apoptosis of animals. The proteinase is synthesized as an inactive proenzyme, which is activated self-catalytically following cleavage at specific aspartate cleavage sites. To clarify whether VPE has the same enzymatic characteristics as caspase-1, we expressed VPE in insect cells and investigated the activation/maturation mechanism of VPE (2). Recombinant VPE exhibited a caspase-1 activity, which is comparable to mammalian caspase-1. The VPE precursor was self-catalytically converted into the mature form exhibiting caspase-1 activity. These in vitro analyses indicate that VPE is the proteinase that exhibits a caspase-1activity.
(1) Hatsugai et al., 305, 855-858 (2004) Science
(2) Kuroyanagi et al., 43, 143-151 (2002) Plant Cell Physiol.