ROLE OF INORGANIC POLYPHOSPHATE IN METABOLISM

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These investigations have as their ultimate objective the elucidation of the role of inorganic polyphosphates (Poly P) in metabolism. A method has been devised by which the undegraded native Poly P can be isolated from Propionibacterium shermanii and the enzymes, Poly P kinase and Poly P glucokinase have been isolated. A procedure has been developed for sizing Poly P up to chain lengths 700. Further studies will consist of six parts: (1) Poly P kinase: The three phases of polymer synthesis, initiation, elongation and termination will be investigated. The elongation has been shown to be a processive mechanism, i.e., the synthesis occurs without release from the enzyme until a chain length of about 725 phosphates is reached. For initiation, Pi and short chain Poly P will be used as primers. Preliminary results indicate short Poly P serves as a primer and the resulting long chain is end labeled. The length varies if the concentration of the primer is varied. A method is proposed using a [32P] Poly P primer to determine the length of Poly P synthesized and for study of termination. (2) Poly P glucokinase: This enzyme catalyzes phosphorylation of glucose with both Poly P and ATP, the activity being 4 times greater with Poly P. Inhibition studies will be done to determine if ATP and Poly P occupy the same active site on the enzyme. For study of the processive process, long chain Poly P end labeled with a 32P-primer will be used as a substrate. If the mechanism is processive, 50% of the glucose should be phosphorylated by the labeled end. This prediction will be tested. (3) Poly P glucokinase combines with the full length of Poly P and Poly P kinase probably at one end only. Electron microscopy will be used to observe how long chain Poly P combines with the enzymes. (4) A method for determination of the molecular weight of Poly P will be developed based on the relative rate of migration during electrophoresis of Poly P and DNA of different sizes. (5) Studies with P. shermanii: The radioactivity of the Poly P, glucose-6-P and ATP will be measured using cells in which the Poly P has been labeled with 32Pi as a method of determining if the phosphorylation of glucose by Poly P occurs physiologically. Polyphosphatase will be isolated and characterized. (6) Poly P in animal cells: The size and content of Poly P in hepatic nuclei during various stages of regeneration will be determined and its interaction with protein examined. Poly P kinase will be isolated and characterized if present. The possible relationship between Poly P in nuclei and the rate of nuclear transcription will be examined.