Fractionation of Leuconostoc mesenteroides NRRL B-512F dextran sucrase by polyethylene glycol: a simple and effective method purification

Abstract

Leuconostoc mesenteroides NRRL B-512F dextran sucrase (sucrose: 1,6-α- d-glucan 6-α- d-glucosyltransferase EC 2.4.1.5) (1.4 U/ml culture supernatant, specific activity 0.58 U/mg protein) was subjected to fractionation by polyethylene glycol (PEG) of different molecular weights. PEG 400 selectively gave greater specificity of precipitation than PEG of higher molecular weights. In a single step precipitation, at a final concentration of 33% (v/v) PEG 400, the enzyme gave the maximum specific activity (8.7 U/mg protein) and in the three successive steps of precipitation it gave 29 U/mg protein specific activity with 50 fold purification. Multiple forms of the extracellular dextran sucrase were characterized by SDS-polyacryline gel electrophoresis. The enzyme exhibited oligomeric forms containing 64, 126 and 188 kDa proteins. Purified dextran sucrase after three successive steps of fractionation by 33% (v/v) PEG 400 gave a single band of protein corresponding to 188 kDa.