By constructing DNA probes we have identified and cloned a human PtdIns 4-kinase, PI4K230, corresponding to a mRNA of 7.0 kb. The cDNA encodes a protein of 2044 amino acids. The C-terminal part of ca. 260 amino acids represents the catalytic domain which is highly conserved in all recently cloned PtdIns 4-kinases. N-terminal motifs indicate multiple heterologous protein interactions. Human PtdIns 4-kinase PI4K230 expressed in vitro exhibits a specific activity of 58 μmol mg-1 min-1. The enzyme expressed in Sf9 cells is essentially not inhibited by adenosine, it shows a high K(m) for ATP of about 300 μM and it is half-maximally inactivated by approximately 200 nM wortmannin. These data classify this enzyme as type 3 PtdIns 4-kinase. Antibodies raised against the N-terminal part moderately activate and those raised against the C-terminal catalytic domain inhibit the enzymatic activity. The coexistence of two different type 3 PtdIns 4-kinases, PI4K92 and PI4K230, in several human tissues, including brain, suggests that these enzymes are involved in distinct basic cellular functions.
|Number of pages||16|
|Journal||Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids|
|Publication status||Published - Mar 25 1999|
- Human phosphatidylinositol 4-kinase
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology