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Molybdenum-free nitrate reductases from vanadate-reducing bacteria
A N Antipov1, N N Lyalikova, T V Khijniak
1A.N. Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow.
FEBS Letters
|January 12, 1999
Summary
Researchers discovered two novel nitrate reductases in Pseudomonas isachenkovii. These enzymes are unique as they function without molybdenum, with one containing vanadium and the other being vanadium-free.
Area of Science:
- Microbiology
- Biochemistry
- Enzymology
Background:
- Dissimilatory nitrate reductases are crucial enzymes in microbial respiration.
- Most known nitrate reductases utilize molybdenum as a cofactor.
- The existence and characteristics of molybdenum-free nitrate reductases remain largely unexplored.
Purpose of the Study:
- To isolate and characterize novel nitrate reductases from Pseudomonas isachenkovii.
- To determine if these enzymes are molybdenum-free and/or molybdenum cofactor-free.
- To investigate the presence of alternative cofactors like vanadium.
Main Methods:
- Isolation and purification of enzymes from Pseudomonas isachenkovii to electrophoretic homogeneity.
- Spectroscopic and biochemical analyses to determine enzyme composition and cofactor content.
- Functional reconstitution assays using the Neurospora crassa nit-1 mutant apoprotein.
Main Results:
- Two distinct nitrate reductases were purified: a soluble periplasmic and a membrane-bound enzyme.
- Both enzymes were confirmed to be molybdenum-free and molybdenum cofactor-free.
- The periplasmic enzyme contained vanadium, while the membrane-bound enzyme was vanadium-free.
Conclusions:
- Pseudomonas isachenkovii possesses unique molybdenum-free dissimilatory nitrate reductases.
- This study provides the first evidence of molybdenum cofactor-free nitrate reductases.
- The findings expand our understanding of enzymatic diversity in microbial respiration.