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Expression, Purification, Crystallization, and Enzyme Assays of Fumarylacetoacetate Hydrolase Domain-Containing Proteins
Published on: June 20, 2019
Fungal catalases: function, phylogenetic origin and structure
Wilhelm Hansberg1, Rodolfo Salas-Lizana, Laura Domínguez
1Departamento de Biología Celular y del Desarrollo, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, UNAM, Mexico City, Mexico. whansberg@ifc.unam.mx
Archives of Biochemistry and Biophysics
|June 16, 2012
Summary
Fungal catalases, including large-subunit types originating from horizontal gene transfer, exhibit diverse evolutionary paths and functions. Their active site channels and heme modifications are crucial for hydrogen peroxide (H2O2) processing.
Area of Science:
- Biochemistry and Molecular Evolution
- Enzymology
- Fungal Genetics
Background:
- Fungi possess various monofunctional heme-catalases, with filamentous ascomycetes featuring large (L1, L2) and small subunits, while yeasts primarily have small-subunit catalases.
- Large-subunit catalases (L1, L2) differ in inducibility, localization, and function (spore germination vs. growth/differentiation), whereas small-subunit catalases are substrate-inhibited but can be protected by NADPH binding.
- Catalase active sites are deeply buried, requiring specific channels for hydrogen peroxide (H2O2) access and product egress, with observed heme modifications (b to d) under oxidative stress.
Purpose of the Study:
- To elucidate the evolutionary origins and phylogenetic relationships of fungal catalases, particularly large-subunit types.
- To investigate the structural and functional adaptations of fungal catalases, including substrate access channels and heme modifications.
- To analyze the distribution and potential horizontal gene transfer events of catalase genes across fungal lineages.
Main Methods:
- Phylogenetic analysis of fungal catalases to infer evolutionary history and identify horizontal gene transfer events.
- Bioinformatic analysis of protein sequences to predict functional elements like secretion signal peptides and peroxisomal localization signals.
- Molecular dynamics simulations to study the interaction of H2O2 with the active site channel and the role of specific amino acid residues.
- Biochemical characterization of catalase modifications, including heme transformations and covalent bonding under oxidative stress.
Main Results:
- Phylogenetic analysis suggests large-subunit catalases originated from one or two horizontal gene transfers from Actinobacteria to an early fungal ancestor.
- Horizontal gene transfer events were also detected for small- and large-subunit catalases in other fungi, including bacteria to Malassezia globosa.
- L2-type catalases possess secretion signals, are induced by stressors, and are crucial for growth, while L1-type catalases lack signals and are vital for spore germination.
- Fungal small-subunit catalases show evolutionary links to animal and plant catalases, with some bacterial origins identified.
- Molecular dynamics revealed a dynamic active site channel that widens in the presence of substrate, facilitating H2O2 entry and retention.
- Heme b to heme d transformation and covalent modifications of active site residues occur in vivo and in vitro, particularly under oxidative stress conditions involving singlet oxygen.
Conclusions:
- Fungal catalases exhibit a complex evolutionary history shaped by horizontal gene transfer and lineage-specific adaptations.
- The structural features of catalase active site channels and heme modifications are critical for their enzymatic function and response to oxidative stress.
- Despite extensive study, significant knowledge gaps remain regarding fungal catalases, necessitating further research employing diverse methodologies.
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