Inositol (1,4,5) trisphosphate (Ins(1,4,5)P3) is a well-known messenger molecule that releases calcium from intracellular stores. Homologues with up to six phosphates have been characterized and recently, homologues with seven or eight phosphate groups, including pyrophosphates, have been identified. These homologues are diphosphoinositol pentakisphosphate (PP-InsP5/InsP7) and bis(diphospho)inositol tetrakisphosphate (bis-PP-InsP4/InsP8) , the rapid turnover of which  is regulated by calcium  and adrenergic receptor activity . It has been proposed that the high-energy pyrophosphates might participate in protein phosphorylation . We have purified InsP6 kinase  and PP-InsP5 kinase , both of which display ATP synthase activity, transferring phosphate to ADP. Here, we report the cloning of two mammalian InsP6 kinases and a yeast InsP6 kinase. Furthermore, we show that the yeast protein, ArgRIII, is an inositol-polyphosphate kinase that can convert InsP3 to InsP4, InsP5 and insP6. We have identified a new family of highly conserved inositol-polyphosphate kinases that contain a newly identified, unique consensus sequence.
ASJC Scopus subject areas
- Biochemistry, Genetics and Molecular Biology(all)
- Agricultural and Biological Sciences(all)