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

Whitfield, Hayley L., Sprigg, Colleen, Riley, Andrew M., Potter, Barry V. L., Kuo, Hui-Fen and Brearley, Charles A. (2025) A minimum catalytic unit for synthesis of InsP6 and 5-PP-InsP5 in Arabidopsis. Biochemical Journal, 482 (24). 1815–1830. ISSN 0264-6021

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Abstract

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 pyrophosphates, inositol tris/tetrakisphosphate (ITPK)1 and Arabidopsis thaliana diphosphoinositol pentakisphosphate kinase (VIH)1/VIH2 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 the combination of ITPK1 and inositol pentakisphosphate 2-kinase (IPK1) is sufficient to synthesize 5-PP-InsP5 from 1D-myo-inositol 3-monophosphate (Ins3P) and that ITPK1 is capable of converting 1D-myo-inositol 1-monophosphate to myo-inositol 1,3,4,5,6-pentakisphosphate [Ins(1,3,4,5,6)P5]. In defining a minimal catalytic unit for synthesis of both myo-inositol 1,2,3,4,5,6-hexakisphosphate (InsP6/Ins(1,2,3,4,5,6)P6) and 5-PP-InsP5, we define the minimum enzymology of the 'lipid-independent' pathway of InsP6 synthesis from Ins3P and its intermediates. The pathway proceeds: Ins3P, 1D-myo-inositol 3,4-bisphosphate, 1D-myo-inositol 3,4,5-trisphosphate, 1D-myo-inositol 3,4,5,6-tetrakisphosphate, Ins(1,3,4,5,6)P5, Ins(1,2,3,4,5,6)P6, and therefrom to 5-diphosphoinositol-1,2,3,4,6-pentakisphosphate [5-PP-Ins(1,2,3,4,6)P5].

Item Type:	Article
Additional Information:	Data Availability: The authors affirm that all data supporting the findings of the study are available within the article and supplementary material. Funding information: HLW was supported by the NERC, UK, through NE/W000350/1. CS was supported by a BBSRC Norwich Research Park Doctoral Training Studentship (Ref. BB/M011216/1). This work was funded in part by The Wellcome Trust. BVLP is a Wellcome Trust Senior Investigator.
Uncontrolled Keywords:	cell biology,inositol,phosphate,molecular biology,biochemistry,cell biology ,/dk/atira/pure/subjectarea/asjc/1300/1312
Faculty \ School:	Faculty of Science > School of Biological Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Plant Sciences Faculty of Science > Research Groups > Molecular Microbiology
Related URLs:	http://www.scopus.com/inward/record.url?... https://portlandpress.com/biochemj/artic...
Depositing User:	LivePure Connector
Date Deposited:	17 Nov 2025 16:30
Last Modified:	22 Dec 2025 11:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/101046
DOI:	10.1042/BCJ20253161

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