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Catalytic Properties of Phosphoglucomutase from Pea Chloroplasts

L. V. Matasova and T. N. Popova*

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 July 27, 1998; Revision received March 3, 1999
Electrophoretically homogeneous phosphoglucomutase (PGM) with specific activity of 3.6 units/mg protein was isolated from pea (Pisum sativum L.) chloroplasts. The molecular mass of this PGM determined by gel-filtration is 125 ± 4 kD. According to SDS-PAGE, the molecular mass of subunits is 65 ± 3 kD. The Km for glucose-1-phosphate is 18.0 ± 0.5 µM, and for glucose-1,6-diphosphate it is 33 ± 0.7 µM. At glucose-1-phosphate and glucose-1,6-diphosphate concentrations above 0.5 and 0.2 mM, respectively, substrate inhibition is observed. The enzyme has optimum activity at pH 7.9 and 35°C. Mg2+ activates the PGM. Mn2+ activates the enzyme at concentrations below 0.2 mM, while higher concentrations have an inhibitory effect. The activity of the PGM is affected by 6-phosphogluconate, fructose-6-phosphate, NAD+, ATP, ADP, citrate, and isocitrate.
KEY WORDS: phosphoglucomutase, pea chloroplasts