EVIDENCE THAT THE RECENTLY DISCOVERED HIGH-ENERGY NUCLEOTIDE DERIVATIVE, OLIGO(PHOSPHOGLYCEROYL-ATP) FORMS THE END CHAINS OF PURINOGEN, A COMPLEX POLYMERIC MAJOR STORAGE FORM OF ADENINE-NUCLEOTIDE AND PHOSPHATE IN HEART

Previous work in our laboratory has shown that free adenine nucleotides in heart, liver and kidney exchange rapidly with a major acid-insoluble species which we have characterised as oligo[3-pho spho-glyceroyl-gamma-triphospho(5')adenosine(3')], abbreviated to (PG-ATP)(n). This has been found in liver and in heart to be complexed to a specific 3'-phosphodiesterase which releases PG-ATP monomers and is located in mitochondrial inter-membrane space. In [C-14] adenosine-perfused hearts, (PG-ATP)(n) has been shown to reach specific radioactivity equilibrium with free ATP within 30 min. Attempts to estimate the quantities of nucleotide in (PG-ATP)(n) and free nucleotides in response to a variety of stimuli using previously labelled hearts showed by contrast that the free and sequestered nucleotide pools were not at equilibrium. Re-examination of the rapidly labelled acid-insoluble species led to the recognition of radioactive inhomogeneity and of three additional nucleotide components. Perfusion of hearts with phosphate-free medium increased the proportion of C-14 incorporated into the sequestered form by 70% and caused the net transfer of 0.9 mu mol g(-1) of purine from free adenine nucleotides to the sequestered form. The findings point to the existence of a more complex polymer whose rapidly exchanging end chains we had previously isolated and characterised as (PG-ATP)(n); we suggest the name purinogen for this polymer and show that it can contain between 25% and 55% of the tissue nucleotide pool in rat heart.