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J Bacteriol. 1962 May; 83(5): 1047-1057
Copyright © 1962, The Williams & Wilkins Company. All Rights Reserved.

DEPLETION AND REPLENISHMENT OF THE INORGANIC POLYPHOSPHATE POOL IN NEUROSPORA CRASSA¹

^a Department of Experimental Chemistry, Division of Research and Laboratories, National Jewish Hospital at Denver, Denver, Colorado

ABSTRACT

HAROLD, F. M. (National Jewish Hospital, Denver, Colo.). Depletion and replenishment of the inorganic polyphosphate pool in Neurospora crassa. J. Bacteriol. 83:1047–1057. 1962.—Turnover of the inorganic polyphosphate pool of Neurospora crassa was demonstrated in both growing and nongrowing mycelium. In nitrogen-deficient cultures, polyphosphate synthesis and degradation were in balance and no net changes occurred. When mycelium was suspended in a growth medium deficient in phosphate, polyphosphate was degraded to acid-soluble compounds, including adenosine triphosphate (ATP) and orthophosphate; net synthesis of nucleic acids and phospholipids occurred at the expense of polyphosphate. Various attempts were made to demonstrate direct formation of ATP from polyphosphate when oxidative and fermentative ATP generation were blocked. No evidence for this reaction could be obtained, suggesting that the primary product of polyphosphate degradation is not ATP but probably orthophosphate.

Addition of phosphate to phosphate-starved mycelium induced rapid replenishment of the polyphosphate pool; polyphosphate accumulation ceased abruptly when the original level had been restored. The finding that ATP accumulation within the mycelium preceded polyphosphate synthesis, together with the rapid turnover of this compound, supports the view that ATP is the metabolic precursor of polyphosphate.

The results suggest a cyclic pattern of polyphosphate metabolism. In N. crassa at least, polyphosphate does not appear to function as a reservoir of "high-energy" phosphate, but the polyphosphate cycle may be involved in the dissipation of excess ATP.

¹ A preliminary report was presented at the 61st Annual Meeting of the American Society for Microbiology, 1961.