Purification and Some Catalytic Properties of Phosphoglucomutase from Maize Leaves

T. N. Popova^*, L. V. Matasova, and A. A. Lapot’ko

Department of Plant Physiology and Biochemistry, Voronezh State University, Universitetskaya pl. 1, Voronezh, 394693 Russia; E-mail: root@bc.vsu.ru

^* To whom correspondence should be addressed.

Received October 28, 1997; Revision received January 13, 1998

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Phosphoglucomutase (EC 2.7.5.1, PGM) was purified to homogeneity from maize (Zea mays L.) leaves. The enzyme had specific activity 11.7 U/mg protein and molecular mass (determined by gel-chromatography) of 133 ± 4 kD. The molecular mass of PGM subunits determined by SDS-electrophoresis was 66 ± 3 kD. The enzyme had K_m for glucose-1-phosphate and glucose-1,6-diphosphate of 20.0 ± 0.9 and 16.0 ± 0.8 µM, respectively. Concentrations of glucose-1-phosphate and glucose-1,6-diphosphate above 3 and 0.4 mM, respectively, cause substrate inhibition. The enzyme activity was maximal at pH 8.0 and temperature 35°C. Magnesium ions activate the enzyme and manganese ions inhibit it. 3-Phosphoglycerate is an uncompetitive inhibitor of the enzyme (K_i = 1.22 ± 0.05 mM). Fructose-6-phosphate, 6-phosphogluconate, and ADP activate PGM, whereas ATP, UTP, and AMP inhibit the enzyme. Citrate was also a potent inhibitor, inhibitory effects of isocitrate and cis-aconitate being less pronounced.

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KEY WORDS: phosphoglucomutase, purification, regulation of activity, maize leaves

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