ROLE OF INORGANIC POLYPHOSPHATE IN METABOLISM

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It has been known for many years that inorganic polyphoshates (Poly P), which consist of linear anhydrides of phoshate varying in length from 3 to more than 200 phosphate residues, are present in microorganisms and also in higher animals. The role of the polyphosphates in metabolism is largely unknown. The object of this research is to investigate the role of Poly P in propionic acid bacteria and in other cells, if developments are such as to indicate this is desirable. The propionic acid bacteria are particularly suitable for such studies since we have shown that they utilize inorganic pyrophosphate (PPi) in certain reactions in place of ATP and it seems likely they likewise may utilize Poly P. The investigation will be divided into 3 broad categories. 1. Comparison of the roles of ATP, PPi and Poly P in reactions of the propionic acid bacteria. 2. Poly P glucokinase: structure, specificity and mechanism of catalysis. 3. Turnover of Poly P in the propionic acid bacteria. Item 1. will consist of measurement of the relative rates of reactions with the three phosphate compounds with the purpose of determining whether or not Poly P has a role which has not yet been discovered and in particular the most likely source of Poly P. Item 2. concerning Poly P-glucokinase will be a continuation of preliminary work which has shown this enzyme is abundant in the propionic acid bacteria. The structure and specificity of the enzyme will be investigated and the mechanism of catalysis, i.e., whether or not the mechanism is processive or random. Item 3., the measurement of turnover of Poly P will involve 32p labeling in vivo and in vitro and measurements of the rate of labeling of the Poly P. These results should provide an answer to the question of whether or not Poly P has a central role in metabolism.