Heme Protein Biogenesis - Catalase in Enterococcus faecalis
Författare
Summary, in Swedish
Popular Abstract in English
Heme is a small red-colored molecule consisting of an iron atom bound to a chemical structure called porphyrin. Heme is essential for many organisms, including humans, because it is a cofactor in a variety of proteins that are needed to sustain metabolism. The probably most famous heme protein is hemoglobin which gives blood its red color. The heme cofactor in hemoglobin binds oxygen to be distributed in the body.
Besides the binding of oxygen heme can confer a protein with one of several other functions. Those are certain chemical reactions needed for the degradation of toxic compounds, the transport of electrons needed for generation of energy from nutrients, and the sensing of oxygen enabling organisms to adapt their metabolism.
Despite the importance of heme proteins in nature we still do not understand how they are produced in cells, i.e. by what mechanisms the heme group becomes inserted into proteins. One well-studied heme protein is catalase. This protein is responsible for the degradation of toxic hydrogen peroxide in many organisms. Catalase enzymes of many diverse organisms, e.g. bacteria and mammals, are very similar. In this work we have used the bacterium Enterococcus faecalis as a simple model organism to study how catalase is produced and how important this enzyme is for survival of the bacterium.
Catalase is made up of four identical protein subunits that are combined to a functional enzyme in a complex fashion. One heme molecule is placed into each of the four subunits. The research work of this thesis comprises cellular processes needed for formation of functional catalase enzyme.
E. faecalis is resistant to high concentrations of hydrogen peroxide. The reason for that is that this bacterium in addtition to catalase produces several enzymes that degrade hydrogen peroxide. The contribution of catalase to protection against hydrogen peroxide was studied.
The findings presented in this thesis increase our knowledge about the cellular processes needed for production of a heme protein. They also contribute to a better understanding of lactic acid bacteria including E. faecalis which is used within the food industry and which is an opportunistic pathogen that under certain circumstances can cause severe infections.
Heme is a small red-colored molecule consisting of an iron atom bound to a chemical structure called porphyrin. Heme is essential for many organisms, including humans, because it is a cofactor in a variety of proteins that are needed to sustain metabolism. The probably most famous heme protein is hemoglobin which gives blood its red color. The heme cofactor in hemoglobin binds oxygen to be distributed in the body.
Besides the binding of oxygen heme can confer a protein with one of several other functions. Those are certain chemical reactions needed for the degradation of toxic compounds, the transport of electrons needed for generation of energy from nutrients, and the sensing of oxygen enabling organisms to adapt their metabolism.
Despite the importance of heme proteins in nature we still do not understand how they are produced in cells, i.e. by what mechanisms the heme group becomes inserted into proteins. One well-studied heme protein is catalase. This protein is responsible for the degradation of toxic hydrogen peroxide in many organisms. Catalase enzymes of many diverse organisms, e.g. bacteria and mammals, are very similar. In this work we have used the bacterium Enterococcus faecalis as a simple model organism to study how catalase is produced and how important this enzyme is for survival of the bacterium.
Catalase is made up of four identical protein subunits that are combined to a functional enzyme in a complex fashion. One heme molecule is placed into each of the four subunits. The research work of this thesis comprises cellular processes needed for formation of functional catalase enzyme.
E. faecalis is resistant to high concentrations of hydrogen peroxide. The reason for that is that this bacterium in addtition to catalase produces several enzymes that degrade hydrogen peroxide. The contribution of catalase to protection against hydrogen peroxide was studied.
The findings presented in this thesis increase our knowledge about the cellular processes needed for production of a heme protein. They also contribute to a better understanding of lactic acid bacteria including E. faecalis which is used within the food industry and which is an opportunistic pathogen that under certain circumstances can cause severe infections.
Avdelning/ar
Publiceringsår
2012
Språk
Engelska
Dokumenttyp
Doktorsavhandling
Förlag
Department of Biology, Lund University
Ämne
- Biological Sciences
Nyckelord
- Enterococcus faecalis
- heme proteins
- protein assembly
- oxidative stress
- catalase
- cytochrome
Status
Published
Handledare
ISBN/ISSN/Övrigt
- ISBN: 978-91-7473-288-7
Försvarsdatum
12 april 2012
Försvarstid
09:30
Försvarsplats
Biology Building Lecture Hall, Sölvegatan 35, 223 62 Lund
Opponent
- Axel Hartke (Dr.)