Apaf-1-interacting protein (APIP) is known to inhibit two different types of cell death: caspase-1-dependent pyroptosis and caspase-9-dependent apoptosis. APIP is also involved in the methionine-salvage pathway, where it is called 5-methylthioribulose-1-phosphate dehydratase (MtnB). The enzyme activity seems to be essential for inhibition of pyroptosis by APIP, but not for inhibition of apoptosis. In this study, human APIP was overproduced in Escherichia coli, purified and crystallized. An X-ray diffraction data set was collected to 2.40 Å resolution and the crystals belonged to space group C222(1), with unit-cell parameters a=106.61, b=107.50, c=189.76 Å. Given that four APIP molecules exist in the asymmetric unit, the Matthews coefficient is 2.70 Å3 Da(-1) and the corresponding solvent content is 54.4%.