Purification and multiple forms of phosphoglucomutase from potato tubers

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Abstract
Two fractions (Peaks I and II) having phosphoglucomutase [EC 2.7.5.1] activity were separated by DEAE-cellulose chromatography of the crude enzyme preparation from potato [Solanum tuberosum] tubers. Upon separate rechromatography under the same conditions, they were respectively eluted at the same positions as initially eluted. Incubation of Peaks I and II with glucose 1,6-bisphosphate which should cause conversion of the dephosphorylated form to the phosphorylated form caused no change in their eluting positions in rechromatography. The ratio of their contents in the crude extracts were fairly constant among different samples of potato tubers. Peak I was further separated into 3 fractions on isoelectric focusing. The resulting main fraction was purified 1800-fold over the crude extract with a 9% yield. It was homogeneous as judged by polyacrylamide gel electrophoreses in the absence and presence of sodium dodecyl sulfate. Crude extracts from peas and broad beans each contain a single species of phosphoglucomutase which corresponds on the chromatograph to the Peak II enzyme from potato tubers. Apparently phosphoglucomutase from potato tubers contains at least 2, possibly 4, different protein species.