Purification of alpha-galactosidase from seeds of Sesbania marginata

Abstract

Alpha-galactosidase taken from a raw extract of Sesbania marginata legume seeds was purified by partitioning in aqueous two-phase systems (ATPS). Initially, galactomannan/dextran 2,000,000 systems were used for the purification, and the partition coefficients of a -galactosidase varied from 1.5 to 4.0. However, mass transport in these systems was poor due to the high viscosity of the employed polymers. Therefore, partitioning in polyethyleneglycol (PEG)/ sodium phosphate systems and the effect of sodium chloride upon the enzyme purification and the yield of a -galactosidase were also investigated. The purification achieved in a single-step was 5.7 with a recovery of 144% of a -galactosidase, possibly due to the removal of materials which inhibited a -galactosidase activity before the purification. The removal of the main protein contaminants and the highest yields were achieved in PEG 4,000/ sodium phosphate + 6% NaCl system at pH 5.0. Further purification by preparative on-exchange chromatography was also developed.