inositol hexakisphosphate & diphosphoinositol-pentakisphosphate kinase 1 (insP6 & PP-IP5 kinase 1, PP-IP5 kinase 1, inositol pyrophosphate synthase 1, hsVIP1, IP6 kinase, histidine acid phosphatase domain-containing protein 2A, HISPPD2A, IP6K, IPS1, KIAA0377, PPIP5K1, VIP1)

Function: - bifunctional inositol kinase - catalyzes formation of diphosphoinositol pentakisphosphate (insP7 or PP-insP5) & bi-diphosphoinositol tetrakisphosphate (insP8 or PP2-insP4) - converts inositolitol hexakisphosphate (insP6) to insP7 - also able to convert insP7 to insP8 - probably specifically mediates formation of 4PP-insP5 & 6PP-insP5 insP7 isomers but not of 5PP-IP5 insP7 isomer - activated when cells are exposed to hyperosmotic stress ATP + 1D-myo-inositol hexakisphosphate ADP + 5-diphospho-1D-myo-inositol (1,2,3,4,6)pentakisphosphate ATP + 1D-myo-inositol 1,3,4,5,6-pentakisphosphate ADP + diphospho-1D-myo-inositol tetrakisphosphate (isomeric configuration unknown) ATP + 1D-myo-inositol 5-diphosphate pentakisphosphate ADP + 1D-myo-inositol bisdiphosphate tetrakisphosphate (isomeric configuration unknown) Kinetic parameters: - KM=0.12 uM for insP6 - KM=0.10 uM for insP7 - Vmax=0.03 nmol/min/mg enzyme with insP6 as substrate - Vmax=0.13 nmol/min/mg enzyme with insP7 as substrate Structure: - belongs to the histidine acid phosphatase family, VIP1 subfamily - although related to histidine acid phosphatases, it lacks the conserved active sites, suggesting that it has no phosphatase activity Compartment: cytoplasm, cytosol Alternative splicing: named isoforms=7 Expression: - widely expressed - high expression in skeletal muscle, heart & brain

General

kinase or ATP-phosphotransferase phosphoprotein

Properties

SIZE: entity length = 1433 aa MW = 160 kD COMPARTMENT: cytoplasm MOTIF: Ser phosphorylation site {S475}

Database Correlations

UniProt Q6PFW1 Pfam PF00328 ENZYME correlations

References

UniProt :accession Q6PFW1