Isolation of starch branching enzyme I from potato using γ-cyclodextrin affinity chromatography

This study presents a novel, fast and easy method to isolate starch branching enzyme I (EC 2.4.1.18, SBE-I) from potato (Solanum tuberosum L. cv. ‘Dianella') by γ-cyclodextrin (γ-CD) affinity chromatography of the supernatant obtained after polyethylene glycol 6000 precipitation of the crude homogenate. SBE-I was specifically eluted by competition with free γ-CD. The resulting protein fraction was homogeneous, as analysed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and contained no contaminating hydrolytic activities, as monitored by activity staining using zymograms and specific assays for - and β-amylase. The overall purification was 296-fold and the yield was 38%.