Polyphosphoinositide phospholipase C and evidence for inositol-phosphate-hydrolysing activities in the plasma-membrane fraction from light-grown wheat (Triticum aestivum L.) leaves |
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Authors: | Michael C Arz Hans J Grambow |
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Institution: | (1) Institut für Biologie III, Biochemie der Pflanzen, RWTH Aachen, Worringerweg 1, D-52074 Aachen, Germany |
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Abstract: | The phospholipase C (PLC; EC 3.1.4.3) activity in isolated plasma membranes of light-grown wheat (Triticum aestivum L. cv. Prelude) leaves was investigated. The activity against the polyphosphoinositides was strongly dependent on Ca2+ and was affected by the anionic detergent deoxycholate (DOC). In the presence of 20 M Ca2+ the PLC activity preferred phosphatidylinositol 4,5-bisphosphate (PIP2) over phosphatidylinositol 4-monophosphate (PIP) as a substrate. Instead, with 1 mM Ca2+ the enzyme clearly favoured PIP. In addition, the PIP2-PLC activity was increased by Mg2+ and in the presence of GTP, guanosine 5 -( -thio)-triphosphate as well as ATP, CTP, guanosine 5 -diphosphate and guanosine 5 -( -thio)-diphosphate. Further analysis showed that a molybdate-sensitive phosphatase activity catalysing the dephosphorylation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) is also associated with the plasma-membrane vesicles. Dephosphorylation of Ins(1,4,5)P3 was reduced in the presence of GTP or by inclusion of the unspecific phosphatase inhibitor molybdate. The results indicate the presence of a PIP2-PLC activity and the presence of a molybdate-sensitive phosphatase activity in wheat plasma-membrane vesicles.Abbreviations DOC
deoxycholate
- IDPase
inosine 5 -diphosphatase
- InsPs
inositol phosphates, the numbering at the end indicates the number of phosphate residues and when their positions on the inositol ring are known they are indicated in parentheses, i.e.
- Ins(1,4,5)P3
inositol 1,4,5-trisphosphate
- PIP
phosphatidylinositol 4-monophosphate
- PIP2
phosphatidylinositol 4,5-bisphosphate
- PLC
phospholipase C
This work was financially supported by grant from the Deutsche Forschungsgemeinschaft (DFG). M. C. Arz gratefully acknowledges the support of a Graduiertenstipendium des Landes Nordrhein-Westfalen (Germany). We wish to thank S. Laden and G.E. Grambow for assistance. |
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Keywords: | Phospholipase C Phosphatidylinositol 4 5-bisphosphate Inositol 1 4 5-trisphosphate Plasma membrane Phosphatase Triticum |
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