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Purification and Physical-Chemical Characterization of the Three Hydroperoxidases from the Symbiotic Bacterium Sinorhizobium meliloti
- Source :
- Biochemistry. 43:12692-12699
- Publication Year :
- 2004
- Publisher :
- American Chemical Society (ACS), 2004.
-
Abstract
- Three genes encoding heme hydroperoxidases (katA, katB, and katC) have been identified in the soil bacterium Sinorhizobium meliloti. The recombinant proteins were overexpressed in Escherichia coli and purified in order toachieve a spectral and kinetic characterization. The three proteins contain heme b with high-spin Fe(III). KatB is an acidic bifunctional homodimeric catalase-peroxidase exhibiting both catalase (k c a t = 2400 s - 1 ) and peroxidase activity and having a high affinity for hydrogen peroxide (apparent K M = 1.6 mM). KatA and KatC are acidic monofunctional homotetrameric catalases. Although different in size (KatA is a small subunit catalase while KatC is a large subunit catalase) both enzymes exhibit the same heme type and a similar affinity for H 2 O 2 (apparent K M values of 160 and 150 mM). However, the turnover rate of KatA (k c a t = 279000 s - 1 ) exceeds that of KatC (k c a t = 3100 s - 1 ) significantly. The kinetic parameters are in good agreement with the physiological role of these heme proteins. KatB is the housekeeping hydroperoxidase exhibiting the highest affinity for hydrogen peroxide, while KatA has the lowest H 2 O 2 affinity but the highest k c a t /K M value (1.75 x 10 6 M - 1 s - 1 ), in agreement with the hydrogen peroxide inducibility of the encoding gene. Moreover, the lower catalytic efficiency of KatC (2.1 × 10 4 M - 1 s - 1 ) appears to be enough for growing in the stationary phase and/or under heat or salt stress (conditions that are known to favor katC expression).
- Subjects :
- Hemeprotein
Protoporphyrins
Heme
medicine.disease_cause
Biochemistry
chemistry.chemical_compound
Bacterial Proteins
medicine
catalase-peroxidase
Cloning, Molecular
Symbiosis
Hydrogen peroxide
Escherichia coli
Sinorhizobium meliloti
biology
Electron Spin Resonance Spectroscopy
Hydrogen-Ion Concentration
biology.organism_classification
Recombinant Proteins
Molecular Weight
Kinetics
Heme B
Peroxidases
chemistry
Catalase
Hydroperoxidase
biology.protein
Spectrophotometry, Ultraviolet
Peroxidase
Subjects
Details
- ISSN :
- 15204995 and 00062960
- Volume :
- 43
- Database :
- OpenAIRE
- Journal :
- Biochemistry
- Accession number :
- edsair.doi.dedup.....8d09ca26ea42743217356c5d9a8d1896