A novel human protease similar to the interleukin‐1 beta converting enzyme induces apoptosis in transfected cells

We have identified a novel cDNA encoding a protein (named TX) with > 50% overall sequence identity with the interleukin‐1 beta converting enzyme (ICE) and approximately 30% sequence identity with the ICE homologs NEDD‐2/ICH‐1L and CED‐3. A computer homology model of TX was constructed based on the X‐ray coordinates of the ICE crystal recently published. This model suggests that TX is a cysteine protease, with the P1 aspartic acid substrate specificity retained. Transfection experiments demonstrate that TX is a protease which is able to cleave itself and the p30 ICE precursor, but not to generate mature IL‐1 beta from pro‐IL‐1 beta. In addition, this protein induces apoptosis in transfected COS cells. TX therefore delineates a new member of the growing Ice/ced‐3 gene family coding for proteases with cytokine processing activity or involved in programmed cell death.