The enzyme is very important in the processing of beet sugar, where it is used to remove raffinose which inhibits normal crystallization of sucrose. It is also used in the hydrolysis of raffinose and stachyose present in soymilk, as these sugars cause intestinal discomfort and flatulence and in the processing of legume foods, upgrading their nutritional value. Another possible application of α-galactosidase is seen in pulp and paper industry, where galactosidases could enhance the bleaching effect of endo-β-1,4-mannanases on softwood kraft pulp.

This work purposes the production, purification and characterization of α-galactosidase from Tachigali multijuga seeds. For enzyme production, the pre-germinated seeds during 108 h were frozen, powdered in a blender, resuspended in 100 mM sodium acetate buffer, pH 5.0. The suspension was centrifuged (15,300g) for 40min at 4 ºC. The supernatant was used as a crude enzyme preparation. α-Galactosidase was assayed in a reaction system containing 650µL of 100mM sodium acetate buffer, pH 5.0; 100μL of enzyme preparation; and 250µL of 2mM p-nitrophenyl- α-D-galactopyranoside (pNPGal). The reaction was run for 15 min at 40 ºC and stopped by the addition of 1 mL of 0.5 M sodium carbonate. This enzyme has been purified by acid precipitation and successive chromatographies on DEAE-Sephacel and Sephadex G-150. SDS-PAGE analysis revealed that a single protein with molecular mass of 30 kDa. The optimum pH and temperature were found to be 5.0 and 40 °C, respectively. The enzyme presented very low or no inhibition by sodium, β-mercaptoethanol, sucrose, iodacetamide, glucose, and EDTA, but was highly inhibited by SDS, copper and D-galactose. The K_M and V_max values were determinate to be 0.46mM and 0.48mM.min-1, respectively, for substrate pNPGal. This enzyme showed moderate thermal stability, maintaining 75% of the original activity after 3 hours incubation at 40° C.

Inhibition by D-galactose was found to be competitive and the K_i value was 3,56mM. Support: FAPEMIG /CAPES.