Dipeptidyl peptidase IV (DPP IV, CD26, EC 3.4.14.5) was extracted from ostrich kidney cortex, intact kidney, ileum, pancreas, and liver. DPP IV was purified from the kidney cortex 373-fold by using homogenization, autolysis, diethylaminoethyl-Toyopearl 650 M, Cu2+-chelate affinity, and Mono Q chromatography. Autolysis conditions were investigated and optimized with regards to pH, incubation time, and Triton X-100 concentration. Nondenaturing gradient polyacrylamide gel electrophoresis (PAG) and sodium dodecyl sulfate-PAGE revealed molecular mass values of 270 K and 133 K for the native enzyme and its subunit, respectively. PAG-isoelectrofocusing indicated a pi of 4.7. The pH and temperature optimum were 8.0 and 45 degrees C, respectively. The enthalpy of activation was computed as 20.91 kJ/mol. k(cat) and k(cat)/K-m values were determined for various chromogenic substrates having the sequence of X-Pro-pNA. The effect of several metal ions on DPP IV activity was investigated. The N-terminus was blocked with an agent of unknown identity. The above data as well as the amino acid composition of ostrich DPP IV were compared with those of other mammalian and bacterial species. It appears that, in terms of physical characteristics, ostrich DPP IV correlated with those of other species, whereas chemically and kinetically it exhibited distinct characteristics.