Disclosed are human interleukin-1 .beta. converting enzyme like apoptosis proteases-3 and 4 and DNA (RNA) encoding such polypeptides. Also provided is a procedure for producing such polypeptides by recombinant techniques and antibodies and antagonists against such polypeptides. Also provided are methods of using the polypeptides, for example, as an antitumor agent, and antiviral agent, and antibodies and antagonists against such polypeptides for example, for treating Alzheimer's disease, Parkinson's disease, rheumatoid arthritis and head injury.