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Abstract
Papain was purified from dried Carica papaya latex by fractioned salt precipitation in presence of sodium tetrathionate to preserve enzymatic activity. Purification was followed by different electrophoretic methods. Identification of the purified product was afforded by submitting the peptides obtained by tryptic digestion of papain to matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF/TOF MS) analysis. Comparison of the peptide masses analyzed by peptide mass fingerprinting (PMF) MALDI-TOF and those obtained by theoretical tryptic digestion, revealed the presence of some peptides belonging the other three endopeptidases contained in papaya latex (very similar to papain in molecular weight and pI) in the purified fraction of papain. The PMF by MALDI-TOF could be applied as a method to follow papain purification.
Acknowledgments
The present study was supported by grants from ANPCyT (PICT N° 38088 and PICT N° 02224) and Universidad Nacional de La Plata (Project X-445). C. R. Llerena-Suster was awarded a CONICET fellowship.
Notes
1Theoretical PMF calculated using the Biotools 3.1 software.
2Papain numeration.
a Data obtained from the purified papain without TT.
b Data obtained from the purified papain in presence of TT.
c Theoretical PMF MALDI-TOF calculated using the Biotools 3.1. Software (Bruker Daltonics).
d Papain numeration.
*Carbamidomethylated peptides.
a Papain numeration.
*Carbamidomethylated peptides.
Rows in gray indicate the tryptic peptides coincident with those obtained from the PMF MALDI-TOF of the whole purified papain.