Invertase inhibitor from potatoes: purification, characterization, and reactivity with plant invertases

Invertase inhibitor was extracted from potato tubers and purified nearly 1000-fold. The purification procedure involved precipitation at pH 4.0, fractionation with ammonium sulfate, adsorption on alumina Cγ gel, and gel filtration on Sephadex G-100 and DEAE-Sephadex A-50. The product obtained was homogeneous to electrophoresis on polyacrylamide gel. Exclusion chromatography on Sephadex G-100 indicated a molecular weight of about 17,000. The inhibitor did not inhibit yeast, Neurospora, and several plant invertases. It completely inhibited potato tuber invertase and a number of other plant invertases. Some plant invertases were partially inhibited.