FRACTIONATION OF LEUCONOSTOC-MESENTEROIDES NRRL B-512F DEXTRAN SUCRASE BY POLYETHYLENE-GLYCOL - A SIMPLE AND EFFECTIVE METHOD OF PURIFICATION

Leuconostoc mesenteroides NRRL B-512F dextran sucrase (sucrose: 1,6-al pha-D-glucan 6-alpha-D-glucosyltransferase EC 2.4.1.5) (1.4 U/ml cultu re supernatant, specific activity 0.58 U/mg protein) was subjected to fractionation by polyethylene glycol (PEG) of different molecular weig hts. PEG 400 selectively gave greater specificity of precipitation tha n PEG of higher molecular weights. In a single step precipitation, at a final concentration of 33% (v/v) PEG 400, the enzyme gave the maximu m specific activity (8.7 U/mg protein) and in three successive steps o f precipitation it gave 29 U/mg protein, specific activity with 50 fol d purification. Multiple forms of the extracellular dextran sucrase we re characterized by SDS-polyacrylamide gel electrophoresis. The enzyme exhibited oligomeric forms containing 64, 126 and 188 kDa proteins. P urified dextran sucrase after three successive steps of fractionation by 33% (v/v) PEG 400 gave a single band of protein corresponding to 18 8 kDa.