Observation of inositol pentakis- and hexakis-phosphates in mammalian tissues by 31P NMR

In analyzing the 31P NMR spectra of extracts of mammalian tissues and cells we have identified inositol pentakis- and hexakis-phosphates in essentially all of the samples examined. These compounds were present at concentrations of at least 5-15 microM. While the sources and functions of these compounds in mammalian cells are not clear, they may play an important role in phosphoinositol metabolism. For example, one obvious possibility is that these compounds may be sources of or sinks for the Ca++ mobilizing inositol tris- and tetrakis-phosphates.