Partial purification and some properties of β-phosphoglucomutase from Lactobacillus brevis
A phosphoglucomutase (β-phosphoglucomutase) specific for β-glucose 1-phosphate, which catalyzes the β-glucose 1-phosphate:glucose 6-phosphate interconversion, was 560-fold purified from Lactobacillus brevis strain L6. The isoelectric point of β-phosphoglucomutase was 3.8 and it had an apparent molec...
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| Autores principales: | , , , |
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| Formato: | JOUR |
| Materias: | |
| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_00039861_v228_n2_p592_Marechal |
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| Sumario: | A phosphoglucomutase (β-phosphoglucomutase) specific for β-glucose 1-phosphate, which catalyzes the β-glucose 1-phosphate:glucose 6-phosphate interconversion, was 560-fold purified from Lactobacillus brevis strain L6. The isoelectric point of β-phosphoglucomutase was 3.8 and it had an apparent molecular weight of 29,000 estimated by gel chromatography. The enzyme required a divalent cation (Mn2+ > Mg2+ > Ni2+ > Co2+) and β-glucose 1,6-bisphosphate for activity. The equilibrium constant Ke for the reaction β-d-glucose 1-phosphate γ d-glucose 6-phosphate at 30 °C and pH 6.7 is 18.5. β-phosphoglucomutase had a pH optimum between 6.3 and 6.8 and appeared to be quite specific: α-glucose 1-phosphate, α- or β-galactose 1-phosphate and α- or β-N-acetylglucosamine 1-phosphate did not substitute for β-glucose 1-phosphate. Double reciprocal plots of the data from initial velocity studies at five β-glucose 1-phosphate concentrations (10 to 100 μm) and four β-glucose 1,6-bisphosphate concentrations (0.125 to 1.0 μm) showed that the apparent Michaelis constants for β-glucose 1-phosphate and β-glucose 1,6-bisphosphate were related to the concentrations of β-glucose 1,6-bisphosphate and β-glucose 1-phosphate, respectively, in such a way as to suggest a pingpong mechanism. The same conclusion was obtained when substrate-velocity relationships were investigated at fixed ratio of both substrates: the Lineweaver-Burk plots showed linear lines and no parabolic ones. The "true" Km for β-glucose 1-phosphate and β-glucose 1,6-bisphosphate were found to be about 12 and 0.8 μm, respectively. © 1984. |
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