Purified Inositol Hexakisphosphate Kinase is an ATP Synthase: Diphosphoinositol Pentakisphosphate as a High-Energy Phosphate Donor

• Published in: Proceedings of the National Academy of Sciences - PNAS 1996-04, Vol.93 (9), p.4305-4310
• Main Authors: Voglmaier, Susan M., Bembenek, Michael E., Kaplin, Adam I., Dormán, György, Olszewski, John D., Prestwich, Glenn D., Snyder, Solomon H.
• Format: Article
• Language: English
• Subjects: Animals; Biochemistry; Chromatography, Gel; Chromatography, Ion Exchange; Creatine; Diphosphates; Enzyme activity; Enzyme Inhibitors - pharmacology; Enzymes; Gels; Heparin; Hydrolysis; Inositol Phosphates - metabolism; Inositol Phosphates - pharmacology; Inositols; Kinetics; Male; Phosphates; Phosphotransferases (Phosphate Group Acceptor) - isolation & purification; Phosphotransferases (Phosphate Group Acceptor) - metabolism; Prosencephalon - enzymology; Proton-Translocating ATPases - metabolism; Rats; Rats, Sprague-Dawley; Substrate Specificity
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.93.9.4305

Diphosphoinositol pentakisphosphate (PP-IP5) and bis(diphospho)inositol tetrakisphosphate (bis-PP-IP4) are recently identified inositol phosphates that possess pyrophosphate bonds. We have purified an inositol hexakisphosphate (IP6) kinase from rat brain supernatants. The pure protein, a monomer of 54 kDa, displays high affinity (Km = 0.7 μ M) and selectivity for inositol hexakisphosphate as substrate. It can be dissociated from bis(diphospho)inositol tetrakisphosphate synthetic activity. The purified enzyme transfers a phosphate from PP-IP5 to ADP to form ATP. This ATP synthase activity indicates the high phosphate group transfer potential of PP-IP5 and may represent a physiological role for PP-IP5.