The control of cellular adenine nucleotides: the discovery and metabolism of an oligomeric derivative of ATP and phosphoglyceric acid in mitochondrial intermembrane space.

The observation of large systematic variations in the purine nucleotides in perfused rat hearts inexplicable by known metabolic transformations led us to propose the existence of some unknown major form of nucleotide. Radiolabelling studies located a rapidly metabolized TCA/methanol-insoluble species in heart, kidney and liver which selective digestion and chromatography allied to 31P-nmr and mass spectrometry suggested to be a tetraphosphate derivative of adenosine and phosphoglyceric acid of the form p3Gri1p[pp5'p3Gri1p]npp5'A, oligo-phosphoglyceroyl-ATP. Partial chemical synthesis has confirmed this basic structure. We have shown that substantial amounts of oPG-ATP are located in liver mitochondrial intermembrane space tightly bound to a specific 3' phosphodiesterase which releases the monomer p3Gri1ppp5'A. Here we show that oPG-ATP is remarkably stabilized by Mg2+ ions and describe the 300-fold purification of the stable substrate-free form of the 3' phosphodiesterase; it has an apparent M(r) = 165k with possibly up to 4 subunits of M(r) = 42.5k, 41.9k, 40.5k and 38.9k. The potential function of oPG-ATP is briefly discussed.