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Published on: October 4, 2017
Thiocalsin: a thioredoxin-linked, substrate-specific protease dependent on calcium.
I Besse1, J H Wong, K Kobrehel
1Department of Plant Biology, University of California, Berkeley 94720, USA.
Summary
Researchers discovered thiocalsin, a calcium-activated protease. It requires reductive activation by thioredoxin (a protein regulating redox activity) to break down wheat storage proteins, aiding germination.
Area of Science:
- Biochemistry
- Plant Science
- Enzymology
Background:
- Thioredoxin is a key protein in redox regulation.
- Calcium ions play various roles in cellular processes.
- Proteases are essential for protein degradation and nutrient mobilization.
Purpose of the Study:
- To characterize a novel calcium-activated protease, thiocalsin.
- To elucidate the activation mechanism of thiocalsin.
- To understand the role of thiocalsin in wheat germination.
Main Methods:
- Purification of thiocalsin from germinating wheat grain.
- Enzymatic assays to determine substrate specificity and activation requirements.
- Investigation of the role of thioredoxin and calcium in enzyme activation.
Main Results:
- Thiocalsin is a 14-kDa serine protease activated by calcium following reductive activation by thioredoxin.
- Thioredoxin, via NADPH and NADP-thioredoxin reductase, reduces disulfide bonds in both thiocalsin and its storage protein substrates (gliadins and glutenins).
- Thiocalsin functions independently of calmodulin.
Conclusions:
- Thioredoxin and calcium jointly activate thiocalsin.
- Activated thiocalsin provides amino acids from storage proteins for germination and seedling development.
- This study expands the known functions of thioredoxin and calcium in plants.
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