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Neuroglobin and cytoglobin as potential enzyme or substrate
F Trandafir1, D Hoogewijs, F Altieri
1Department of Physics of the University of Antwerp, Antwerp, Belgium.
Gene
|June 9, 2007
Summary
Neuroglobin and cytoglobin lack significant enzymatic activity but are stabilized by a reducing system in E. coli. This system, using NADH or NADPH, maintains neuroglobin
Area of Science:
- Biochemistry
- Molecular Biology
- Protein Chemistry
Background:
- Neuroglobin and cytoglobin are heme-containing proteins with incompletely understood functions.
- Their potential enzymatic activities and roles as substrates in enzymatic reactions warrant investigation.
- Understanding their redox states is crucial for elucidating their biological roles.
Purpose of the Study:
- To investigate the enzymatic activities of neuro- and cytoglobin.
- To explore their potential function as substrates in enzymatic reactions.
- To identify factors influencing the redox state of the heme iron in neuroglobin.
Main Methods:
- Assays for superoxide dismutase, catalase, and peroxidase activities.
- Reduction of neuroglobin's disulfide bond (CD7-D5) using thioredoxin reductase.
- In vivo and in vitro studies of Escherichia coli cell extracts.
- Analysis of heme iron reduction in neuroglobin using NADH and NADPH as co-factors.
- Testing the reducing system's specificity on other globins (cytoglobin, myoglobin) and eukaryotic extracts.
Main Results:
- Neuro- and cytoglobin exhibit no significant superoxide dismutase, catalase, or peroxidase activities.
- The internal disulfide bond of human neuroglobin is reducible by thioredoxin reductase.
- Escherichia coli possesses an enzymatic system that maintains neuroglobin's heme iron in the Fe(2+) state, preventing autoxidation in the presence of oxygen.
- NADH and NADPH act as co-factors for this reducing system.
- The reducing system is not specific to neuroglobin and can reduce other globins like cytoglobin and myoglobin, and is also present in eukaryotic tissues.
Conclusions:
- Neuro- and cytoglobin primarily function as non-enzymatic proteins.
- A conserved enzymatic reducing system, utilizing low-molecular-weight co-factors like NADH/NADPH, is critical for maintaining the reduced heme iron state in globins.
- This finding has implications for understanding globin function and redox homeostasis in various organisms.
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