Synthesis of polyphosphate by rat liver mitochondria

Abstract

The synthesis and hydrolysis of acid insoluble polyphosphates has been observed in many lower species and the enzymes involved have been partially purified by Kornberg and Hughes. Data also exists indicating that in bacteria under experimental conditions of biosynthetic blockade, e.g., nitrogen deficiency etc., polyphosphates accumulate within cells. Lehninger and others have noted that mammalian mitochondria swell in the presence of mitochondrial substrates and in the absence of ADP but shrink when ATP concentration is maintained at a high level. A reasonable explanation for these observations could be that excess substrate in the absence of adequate concentrations of nucleotide acceptor, activates the turnover of high energy phosphate into a “phosphagen” or polyphosphate pool at a very rapid rate, thus allowing ATP concentration to fall. The data in this report indicate that substrate does markedly stimulate phosphate uptake into a high molecular weight polyphosphate of rat liver mitochondria with a concomitant decrease in ATP concentration.