7tn8

Structural highlights

Function

ITPK1_MAIZE Kinase that can phosphorylate various inositol polyphosphate such as Ins(3,4,5,6)P4 or Ins(1,3,4)P3 and participates in phytic acid biosynthesis in developing seeds (PubMed:12586875, PubMed:32123645). Phosphorylates Ins(3,4,5,6)P4 at position 1 to form Ins(1,3,4,5,6)P5. This reaction is thought to have regulatory importance, since Ins(3,4,5,6)P4 is an inhibitor of plasma membrane Ca(2+)-activated Cl(-) channels, while Ins(1,3,4,5,6)P5 is not (PubMed:12586875). Also phosphorylates Ins(1,3,4)P3 on O-5 and O-6 to form Ins(1,3,4,6)P4, an essential molecule in the hexakisphosphate (InsP6) pathway (PubMed:12586875). Also able to phosphorylate Ins(3,5,6)P3 but not Ins(1,4,5)P3, Ins(2,4,5)P3, Ins(1,3,4,6)P4 nor Ins(1,3,5,6)P4. Has higher specific activity on Ins(3,4,5,6)P4 than Ins(1,3,4)P3 and Ins(3,5,6)P3 (PubMed:12586875). Can also could use Ins(1,2,5,6)P4 as a substrate (PubMed:12586875). Able to add a beta-phosphate to the 3 positions of Ins(1,2,3,4,5)P5 and to add beta-phosphate to InsP6 to yield 5-InsP7, thus exhibiting InsP6 kinase activity (PubMed:35635723). Has also Ins(1,3,4,5,6)P5 phosphatase activity (PubMed:35635723).^{[1] [2] [3]}

References

1. ↑ Shi J, Wang H, Wu Y, Hazebroek J, Meeley RB, Ertl DS. The maize low-phytic acid mutant lpa2 is caused by mutation in an inositol phosphate kinase gene. Plant Physiol. 2003 Feb;131(2):507-15. PMID:12586875 doi:10.1104/pp.014258
2. ↑ Abhijith KP, Muthusamy V, Chhabra R, Dosad S, Bhatt V, Chand G, Jaiswal SK, Zunjare RU, Vasudev S, Yadava DK, Hossain F. Development and validation of breeder-friendly gene-based markers for lpa1-1 and lpa2-1 genes conferring low phytic acid in maize kernel. 3 Biotech. 2020 Mar;10(3):121. PMID:32123645 doi:10.1007/s13205-020-2113-x
3. ↑ Zong G, Shears SB, Wang H. Structural and catalytic analyses of the InsP(6) kinase activities of higher plant ITPKs. FASEB J. 2022 Jul;36(7):e22380. PMID:35635723 doi:10.1096/fj.202200393R