Recombinant Saccharomyces cerevisiae Inositol polyphosphate multikinase (ARG82)

Inositol phosphate kinase with both monophosphoinositol and diphosphoinositol polyphosphate synthase activities. Able to phosphorylate inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) on both the carbon-3 and carbon-6 positions to synthesize inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4) and inositol 1,4,5,6-tetrakisphosphate (Ins(1,4,5,6)P4), and then to subsequently phosphorylate and convert either isomer of InsP4 to inositol 1,3,4,5,6-pentakisphosphate (Ins(1,3,4,5,6)P5). Its predominant in vivo catalytic function is to convert Ins(1,4,5)P3 to Ins(1,4,5,6)P4 to Ins(1,3,4,5,6)P5 via 6- and 3-kinase activities. It can also use Ins(1,3,4,5,6)P5 as a substrate and act as a diphosphoinositol polyphosphate synthase to generate two different isomers of PP-InsP4. Has also a role in transcription regulation. Forms a complex with ARG80, ARG81 and MCM1 (ArgR-MCM1), which coordinates the expression of arginine anabolic and catabolic genes in response to arginine. Recruits ARG80 and MCM21 to stabilize them. Neither the kinase activity nor inositol phosphates are required for the formation of ArgR-MCM1 transciptional complexes on DNA promoter elements and the control of arginine metabolism. In contrast, only the catalytic activity is required for PHO gene repression by phosphate and for NCR gene activation in response to nitrogen availability, indicating a role for inositol pyrophosphates in these controls. Inositol polyphosphates may be involved in the regulation of chromatin remodeling of transcription. Regulates nuclear mRNA export via inositol phosphate metabolism. Also has lipid kinase activity, transforming the lipid inositol phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) into phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3) in the nucleus. Its kinase activity is necessary for the propagation of most [PSI+] prion variants.