Metabolic and signaling properties of an Itpk gene family in Glycine max

Stiles, Amanda R.; Qian, Xun; Shears, Stephen B.; Grabau, Elizabeth A.

doi:10.1016/j.febslet.2008.04.054

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Volume 582, Issue 13 , Pages 1853-1858, 11 June 2008

Metabolic and signaling properties of an Itpk gene family in Glycine max

Edited by Ulf-Ingo Flügge

Amanda R. Stiles
- Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, 413 Price Hall, Blacksburg, VA 24061, United States
- These authors contributed equally to the work.
- Present address: Department of Plant and Microbial Biology, University of California, Berkeley, CA 94704, United States.
Xun Qian
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, NC 27709, United States
- These authors contributed equally to the work.
Stephen B. Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, NIH, DHSS, Research Triangle Park, NC 27709, United States
Elizabeth A. Grabau
- Department of Plant Pathology, Physiology and Weed Science, Virginia Polytechnic Institute and State University, 413 Price Hall, Blacksburg, VA 24061, United States
- Corresponding author. Fax: +1 540 231 7477.

Received 8 April 2008; received in revised form 28 April 2008; accepted 29 April 2008. published online 12 May 2008.

Abstract

We have cloned and characterized four Itpk genes from soybean. All four recombinant Itpk proteins showed canonical Ins(1,3,4)P₃ 5/6-kinase activity, but a kinetic analysis raised questions about its biological significance. Instead, we provide evidence that one alternative biological role for soybean Itpks is to interconvert the Cl⁻ channel inhibitor, Ins(3,4,5,6)P₄, and its metabolic precursor, Ins(1,3,4,5,6)P₅, within a substrate cycle. The soybean Itpks also phosphorylated Ins(3,4,6)P₃ to Ins(1,3,4,6)P₄ which was further phosphorylated to Ins(1,3,4,5,6)P₅ by soybean Ipk2. Thus, soybean Itpks may participate in an inositol lipid-independent pathway of InsP₆ synthesis.