Thiol protease which cleaves IL-1 beta (il1b), releasing the mature cytokine which is involved in a variety of inflammatory processes, and mediates apoptosis (PubMed:12464617, PubMed:30150286). Component of the NLRP1 inflammasome, which plays a crucial role in innate immunity and inflammation (PubMed:30150286). In response to pathogens and other damage-associated signals, recruited to the NLRP1 inflammasome in its precursor form (PubMed:30150286). Its subsequent activation causes the cleavage of pro-il1b into the midformed il1b, which then evetually leads to il1b maturation and secretion in the extracellular milieu (PubMed:30150286). Required for the development of the cartilaginous pharyngeal skeleton (PubMed:12464617). Strict requirement for an Asp residue at position P1 and has a preferred cleavage sequence of Tyr-Val-Ala-Asp-|-. Heterotetramer that consists of two anti-parallel arranged heterodimers, each one formed by a 20 kDa (p20) and a 10 kDa (p10) subunit (Probable). Interacts (via pyrin domain) with pycard (via pyrin domain) (PubMed:12464617, PubMed:29791979, PubMed:30150286). Interacts with caspb (PubMed:29791979). Component of NLRP1 inflammasomes (PubMed:30150286). Inflammasomes are supramolecular complexes that assemble in the cytosol in response to pathogens and other damage-associated signals and play critical roles in innate immunity and inflammation (PubMed:30150286). The NLRP1 inflammasome is composed of the signal sensor nlrp1, and the adapter pycard (asc), which recruit effector pro-inflammatory caspases caspa and/or caspb (PubMed:30150286). The interaction between nlrp1 and pycard is required for the sequential recruitment of caspa and then caspb (PubMed:30150286). Caspa is preferentially recruited first and this causes the cleavage of pro-il1b into the midformed il1b (PubMed:30150286). This is followed by the recruitment of caspb, which is activated and cleaves the midformed il1b resulting in il1b maturation (PubMed:30150286). Interacts with caiap (PubMed:29123523). Co-localizes with pycard, nlrp1 and caspb in the cytoplasm (PubMed:30150286). Co-localizes with pycard at large cytoplasmic aggregates, known as specks (PubMed:12464617, PubMed:30150286). During embryonic development, highly expressed at 8 hours post-fertilization (hpf) (PubMed:28402832). Expressed at the pharyngula stage at 24 hpf and expression is maintained 48 hpf, 72 hpf and to larval day 4 of development at 96 hpf (PubMed:29791492, PubMed:28402832). During this time, expressed in the pharyngeal arches, and in the intestinal bulb at 72 and 96 hpf (PubMed:29791492, PubMed:12464617). Also expressed in the epidermis and mouth at 48 and 72 hpf (PubMed:12464617). Up-regulated in response to pentachlorophenol (PCP), a toxic pollutant (PubMed:28402832). Up-regulated in response to bacterial infection with E.tarda (PubMed:30150286). The two subunits are derived from the precursor sequence by an autocatalytic mechanism. Morpholino knockdown in early embryos results in abnormalities in the development of the cartilaginous pharyngeal skeleton and eventually results in death upon exhaustion of the yolk (PubMed:12464617). Abnormalities include deformed and thinned Meckel's and palatoquadrate cartilages, deformed ceratohyal cartilages and disorganized branchial cartilages (PubMed:12464617). Morpholino knockdown in one- to four-cell stage embryos results in an open mouth phenotype (PubMed:12464617). Morpholino knockdown in one-cell embryos results in reduced survival in response to bacterial infection with E.tarda, but does not decrease caspb activation (PubMed:30150286). Morpholino knockdown in larvae results in no abnormalities in the brain, eyes or pectoral fins (PubMed:12464617). Belongs to the peptidase C14A family.