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Caspases are a family of cysteine proteases with roles in cytokine matur-ation or apoptosis. Caspase-2 was the first pro-apoptotic caspase identified, but its functions in apoptotic signal transduction are still being elucidated. This study examined the regulation of the activity of caspase-2 using recombinant proteins and a yeast-based system. Our data suggest that for human caspase-2 to be active its large and small subunits must be separ-ated. For maximal activity its prodomain must also be removed | ềFEBS Journal Caspase-2 is resistant to inhibition by inhibitor of apoptosis proteins lAPs and can activate caspase-7 Po-ki Ho1 2 3 Anissa M. Jabbour1 2 3 Paul G. Ekert1 4 5 and Christine J. Hawkins1 2 3 1 Murdoch Children s Research Institute Parkville Australia 2 Children s Cancer Centre RoyalChildren s Hospital Parkville Australia 3 Department of Paediatrics University of Melbourne Parkville Australia 4 Department of Neonatology RoyalChildren s Hospital Parkville Australia 5 The Walter and Eliza Hall institute RoyalMelbourne Hospital Parkville Australia Keywords caspase-2 protease caspase-7 S. cerevisiae enzyme activity Correspondence C. Hawkins or P. Ekert Murdoch Children s Research Institute RoyalChildren s Hospital Flemington Road Parkville VIC 3052 Australia Fax 61 3 9345 4993 CH 61 3 9347 0852 PE Tel 61 3 9345 5823 CH 61 3 9345 2548 PE E-mail chris.hawkins@mcri.edu.au paul.ekert@mcri.edu.au Caspases are a family of cysteine proteases with roles in cytokine maturation or apoptosis. Caspase-2 was the first pro-apoptotic caspase identified but its functions in apoptotic signal transduction are still being elucidated. This study examined the regulation of the activity of caspase-2 using recombinant proteins and a yeast-based system. Our data suggest that for human caspase-2 to be active its large and small subunits must be separated. For maximal activity its prodomain must also be removed. Consistent with its proposed identity as an upstream caspase caspase-2 could provoke the activation of caspase-7. Caspase-2 was not subject to inhibition by members of the IAP family of apoptosis inhibitors. Received 10 November 2004 revised 7 January 2005 accepted 18 January 2005 doi 10.1111 j.1742-4658.2005.04573.x The caspases are a family of cysteine proteases that typically cleave their substrates at aspartate residues 1 . Subclassification of family members has been based on various criteria including substrate specificity or structural features. For example caspases-1
