A cDNA cloned from its ability to stimulate inorganic phosphate uptake in Xenopus oocytes (phosphate uptake stimulator (PiUS)) shows significant similarity with inositol 1,4,5-trisphosphate 3-kinase. However, the expressed PiUS protein showed no detectable activity against inositol 1,4,5-trisphosphate, nor the 1,3,4,5- or 3,4,5,6-isomers of inositol tetrakisphosphate, whereas it was very active in converting inositol hexakisphosphate (InsP6) to inositol heptakisphosphate (InsP7). PiUS is a member of a family of enzymes found in many eukaryotes and we discuss the implications of this for the functions of InsP7 and for the evolution of inositol phosphate kinases. Copyright (C) 1999 Federation of European Biochemical Societies.
- Inositol hexakisphosphate kinase
- Inositol trisphosphate kinase
- Phosphate uptake
ASJC Scopus subject areas
- Structural Biology
- Molecular Biology
- Cell Biology