| Caspase 6 and granzyme B efficiently cleave UFD 2 [ k ( cat ) / K ( m ) = ( 4 5 ) 10 10 ( 4 ) M ( 1 ) 10 s ( 1 ) ] at Asp ( 123 ) , whereas caspases 3 and 7 cleave UFD 2 approx . 10 fold less efficiently immediately upstream at Asp ( 109 ) . ^^^ Thus UFD 2 is added to the growing list of proteins with closely spaced caspase and granzyme B cleavage sites , suggesting the presence of a previously unrecognized , conserved motif . ^^^ Full length recombinant UFD 2 exhibited ubiquitin protein ligase ( ' E3 ' ) like ubiquitination activity in vitro , but this activity was abolished in recombinant UFD 2 truncated at the granzyme B / caspase 6 cleavage site . ^^^ Cleavage of UFD 2 by caspases or granzyme B within this putative regulatory N terminal domain might have important functional consequences within the apoptotic cascade . . ^^^ |