Dec 31, 1997

Identification and characterization of the functional amino acids at the active site of the large thioredoxin reductase from Plasmodium falciparum

The Journal of Biological Chemistry
Tim-Wolf GilbergerS Müller

Abstract

The thioredoxin system, composed of the pyridine nucleotide-disulfide oxidoreductase thioredoxin reductase, the small peptide thioredoxin, and NADPH as a reducing cofactor, is one of the major thiol-reducing systems of the cell. Recent studies revealed that Plasmodium falciparum and human thioredoxin reductase represent a novel class of enzymes, called large thioredoxin reductases. The large thioredoxin reductases are substantially different from the isofunctional prokaryotic Escherichia coli enzyme. The putative essential amino acids at the catalytic center of large thioredoxin reductase from P. falciparum were determined by using site-directed mutagenesis techniques. To analyze the putative active site cysteines (Cys88 and Cys93) three mutant proteins were constructed substituting alanine or serine residues for cysteine residues. Further, to evaluate the function of His509 as a putative proton donor/acceptor of large thioredoxin reductase this residue was replaced by either glutamine or alanine. All mutants were expressed in the E. coli system and characterized. Steady state kinetic analysis revealed that the replacement of Cys88 by either alanine or serine and Cys93 by alanine resulted in a total loss of enzymatic activity. ...Continue Reading

  • References16
  • Citations28

References

  • References16
  • Citations28

Citations

Mentioned in this Paper

Thioredoxin Reductase (NADPH)
Alkalescens-Dispar Group
Activated T Cell Autonomous Cell Death
Enzymes, antithrombotic
Placenta Specimen
Amino Acids, I.V. solution additive
Mutagenesis, Site-Directed
Placenta
Spectrophotometry, Atomic
Sulfhydryl Compounds

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