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The 58 kDa mouse selenoprotein is a BCNU-sensitive thioredoxin reductase
S Gromer1, R H Schirmer, K Becker
1Biochemie-Zentrum der Universität Heidelberg, Germany.
FEBS Letters
|July 28, 1997
Summary
Mouse thioredoxin reductase, an enzyme crucial in cancer research, contains selenium, unlike non-vertebrate versions. This enzyme, along with glutathione reductase, is a target for the drug carmustine.
Area of Science:
- Biochemistry
- Enzymology
- Cell Biology
Background:
- Thioredoxin reductase (TrxR) is a key flavoprotein involved in cellular redox homeostasis.
- Selenium is an essential component of some TrxR enzymes, particularly in vertebrates.
- Ehrlich ascites tumour (EAT) cells in mice are a standard model for cancer and malaria research.
Purpose of the Study:
- To isolate and characterize thioredoxin reductase from mouse Ehrlich ascites tumour (EAT) cells.
- To compare mouse EAT cell thioredoxin reductase with glutathione reductase.
- To investigate the selenium content and enzymatic properties of mouse thioredoxin reductase.
Main Methods:
- Isolation and purification of thioredoxin reductase from mouse EAT cells.
- Enzyme kinetics studies using NADPH, DTNB, and E. coli thioredoxin.
- Comparison of thioredoxin reductase and glutathione reductase from EAT cells.
Main Results:
- Mouse EAT cell thioredoxin reductase was isolated and found to contain selenium (1 equivalent per 58 kDa subunit).
- Enzyme kinetics revealed specific K(M) values for NADPH, DTNB, and E. coli thioredoxin.
- Both thioredoxin reductase and glutathione reductase are targets of carmustine (BCNU), but show no immunologic cross-reactivity.
Conclusions:
- Mouse thioredoxin reductase is a selenoprotein, similar to human counterparts but distinct from non-vertebrate enzymes.
- The characterized kinetic parameters provide insights into the enzyme's function.
- Despite both being BCNU targets, thioredoxin reductase and glutathione reductase are immunologically distinct in mouse EAT cells.