description
General Background : MI-HEXAKISPHOSPHATE (phytate, phytic acid) is one of the most prevalent forms of phosphorylated inositols in the cell, with a total concentration of 15-100 μM . It's cellular distribution is not completely known - some of it is soluble, some is "wall-papered" around membranes, while some is bound to proteins . The compound has been proposed to have a number of signaling roles, including regulation of insulin exocytosis , regulation of nuclear mRNA export , binding of the clathrin assembly proteins AP2 and AP3 , inhibition of clathrin cage assembly , and inhibition of serine and threonine protein phosphatases that are thought to regulate L-type Ca2+ channels . About This Pathway Unlike the phytate biosynthetic pathway found in yeast, which proceeds directly from : INOSITOL-1-4-5-TRISPHOSPHATE by a series of successive phosphorylations (see : PWY-6361), the mammalian pathway uses a detour: : INOSITOL-1-4-5-TRISPHOSPHATE is first isomerized to : INOSITOL-1-3-4-TRIPHOSPHATE (via : CPD-506) , and further phosphorylation proceeds from there . The multiplicity of enzymes that catalyze inositol phosphate transformations and the lack of in vivo studies have made determining the pathway difficult. However, as more in vivo results became available, and as the catalytic efficiencies of the enzymes with different substrates were determined, it became clear that the main tetra-phosphate intermediate in the human pathway is : CPD-505 , supporting the pathway presented here

external resources
NCBI:545332
BIOCYC:HUMAN_PWY-6362
PUBMED:1371119
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genes
INPP5A , INPP5B , INPP5D , INPPL1 , ITPK1 , ITPKA , ITPKB , OCRL , SYNJ1 , SYNJ2 , INPP5J , INPP5K , IPPK , ITPKC , IPMK ,