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Studies on phosphoglucomutase and phosphofructokinase from brain Braun, Peter Eric


It has recently been established that the activity of crystalline muscle phosphoglucomutase can be greatly stimulated by preincubation of the enzyme with a Mg++-imidazole complex. This observation has aroused interest in the physiological significance of such a system in the possible cellular control of phosphoglucomutase activity. The present study constitutes, in part, an investigation of the properties of phosphoglucomutase from brain tissue. A procedure for the purification of phosphoglucomutase from beef brain is described. The brain enzyme appears to be similar to that from skeletal muscle. Evidence is also presented which indicates that the "activation" produced by Mg++-imidazole is probably of no physiological importance in brain. This observation is consistent with the more recent reports that the phosphoglucomutase reaction is likely not involved in cellular regulatory mechanisms. It is well established that phosphofructokinase is intimately involved in the cellular regulation of glycolysis and the citric acid cycle. Control mechanisms of the phosphofructokinase reaction in mammalian tissues have been postulated on the basis of the complex kinetics of the enzyme. In yeast, however, two enzymatically interconvertible forms of the enzyme have been reported. Preliminary experiments in this study failed to demonstrate a phosphofructokinase system in brain similar to that found in yeast.

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