A minimum catalytic unit for synthesis of InsP6 and 5-PP-InsP5 in Arabidopsis

Journal article

Inositol pyrophosphates, diphosphoinositol phosphates, are reported agents of phosphate homeostasis, disease resistance and hormone action in plants. Of the enzymes that have been shown to synthesize inositol pyrophophosphates, ITPK1 and VIH1/2 share the ATP-grasp fold – the latter also possesses a phosphatase domain. Among ATP-grasp inositol phosphate kinases, ITPK1 is particularly flexible – phosphorylating equatorial hydroxyls and equatorial phosphates on inositol phosphates. Herein, we show that combination of ITPK1 and IPK1 is sufficient to synthesize 5-PP-InsP5 from Ins3P and that ITPK1 is capable of converting Ins1P to Ins(1,3,4,5,6)P5. In defining a minimal catalytic unit for synthesis of both InsP6 and 5-PP-InsP5, we define the minimum enzymology of the ‘lipid-independent’ pathway of InsP6 synthesis from Ins3P and its intermediates. The pathway proceed Ins3P, Ins(3,4)P2, Ins(3,4,5)P3, 27 Ins(3,4,5,6)P4, Ins(1,3,4,5,6)P5.

Authors: Whitfield, HL; Sprigg, C; Riley, AM; Potter, BVL; Kuo, H-F

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Portland Press
• Journal: Biochemical Journal
• Volume: 482
• Issue: 24
• Pages: 1815–1830
• Publication date: 2025-12-17
• Acceptance date: 2025-11-07
• DOI: 10.1042/bcj20253161
• EISSN: 1470-8728
• ISSN: 0264-6021
• Language: English
• Keywords: proteomics; inositol; cell biology; phosphate; structural biology; inositol phosphates; inositol pyrophosphates; enzymology; organic synthesis; mass spectrometry