Papain from latex of Carica papaya was purified up to matrix-assisted laser desorption= ionization (MALDI) time-of-flight (TOF) mass spectrometry homogeneity by salt precipitation from two different crude extract sources: a refined preparation obtained in our laboratory and a commercial one. Sodium tetrathionate was tested in the purification process to preserve the enzymatic activity of the peptidase. Purification was checked by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis (PAGE) and cation exchange chromatography, using commercial pure papain as standard for a rapid comparison. The best purification yields (3.4%) were obtained in presence of 30 mM sodium tetrathionate for the crude extract prepared in our laboratory. The described purification method proved to be robust and reliable to obtain pure papain on a preparative scale.Centro de Investigación de Proteínas Vegetale
