title: Identification and characterization of a novel inositol hexakisphosphate kinase.
abstract: The inositol pyrophosphate disphosphoinositol pentakisphosphate (PP-InsP(3)/InsP(7)) is formed in mammals by two recently cloned inositol hexakiphosphate kinases, InsP(6)K1 and InsP(6)K2 (Saiardi, A., Erdjument-Bromage, H., Snowman, A. M., Tempst, P., and Snyder, S. H. (1999) Curr. Biol. 9, 1323-1326). We now report the identification, cloning, and characterization of a third InsP(7) forming enzyme designated InsP(6)K3. InsP(6)K3 displays 50 and 45% sequence identity to InsP(6)K1 and InsP(6)K2, respectively, with a smaller mass (46 kDa) and a more basic character than the other two enzymes. InsP(6)K3 is most enriched in the brain where its localization resembles InsP(6)K1 and InsP(6)K2. Intracellular disposition discriminates the three enzymes with InsP(6)K2 being exclusively nuclear, InsP(6)K3 predominating in the cytoplasm, and InsP(6)K1 displaying comparable nuclear and cytosolic densities.
authors.affiliation: Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: A
authors.initials: A
authors.lastname: Saiardi
authors.forename: E
authors.initials: E
authors.lastname: Nagata
authors.forename: H R
authors.initials: HR
authors.lastname: Luo
authors.forename: A M
authors.initials: AM
authors.lastname: Snowman
authors.forename: S H
authors.initials: SH
authors.lastname: Snyder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D001921:Brain / Q000378:metabolism; D002384:Catalysis; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D003001:Cloning, Molecular; D003600:Cytosol / Q000201:enzymology; D018076:DNA, Complementary / Q000378:metabolism; D006801:Humans; D017403:In Situ Hybridization; D007700:Kinetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D017856:Phosphotransferases (Phosphate Group Acceptor) / Q000096:biosynthesis* / Q000737:chemistry* / Q000302:isolation & purification*; D017354:Point Mutation; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D018076:DNA, Complementary; D017856:Phosphotransferases (Phosphate Group Acceptor); C099438:inositol hexakisphosphate kinase