Recombinant human kynureninase (L-kynurenine hydrolase, EC ) was purified to homogeneity (60-fold) from Spodoptera frugiperda (Sf9) cells infected with baculovirus containing the kynureninase gene. The purification protocol comprised ammonium sulfate precipitation and several chromatographic steps, including DEAE–Sepharose CL-6B, hydroxyapatite, strong anionic and cationic separations. The purity of the enzyme was determined by SDS/ PAGE, and the molecular mass verified by MALDI-TOF MS. The monomeric molecular mass of kDa determined was of the predicted molecular mass. A UV absorption spectrum of the holoenzyme resulted in a peak at 432 nm. .