Functional and structural analysis of catalase oxidized by singlet oxygen

Catalases in the pathogenesis of Sporothrix schenckii research

Pathogenic fungal infection success depends on the ability to escape the immune response. Most strategies for fungal infection control are focused on the inhibition of virulence factors and increasing the effectiveness of antifungal drugs. Nevertheless, little attention has been focused on their physiological resistance to the host immune system. Hints may be found in pathogenic fungi that also inhabit the soil. In nature, the saprophyte lifestyle of fungi is also associated with predators that can induce oxidative stress upon cell damage. The natural sources of nutrients for fungi are linked to cellulose degradation, which in turn generates reactive oxygen species (ROS). Overall, the antioxidant arsenal needed to thrive both in free-living and pathogenic lifestyles in fungi is fundamental for success. In this review, we present recent findings regarding catalases and oxidative stress in fungi and how these can be in close relationship with pathogenesis. Additionally, special focus is placed on catalases of Sporothrix schenckii as a pathogenic model with a dual lifestyle. It is assumed that catalase expression is activated upon exposure to H₂O₂, but there are reports where this is not always the case. Additionally, it may be relevant to consider the role of catalases in S. schenckii survival in the saprophytic lifestyle and why their study can assess their involvement in the survival and therefore, in the virulence phenotype of different species of Sporothrix and when each of the three catalases are required. Also, studying antioxidant mechanisms in other isolates of pathogenic and free-living fungi may be linked to the virulence phenotype and be potential therapeutic and diagnostic targets. Thus, the rationale for this review to place focus on fungal catalases and their role in pathogenesis in addition to counteracting the effect of immune system reactive oxygen species. Fungi that thrive in soil and have mammal hosts could shed light on the importance of these enzymes in the two types of lifestyles. We look forward to encouraging more research in a myriad of areas on catalase biology with a focus on basic and applied objectives and placing these enzymes as virulence determinants.

Monofunctional Heme-Catalases

The review focuses on four issues that are critical for the understanding of monofunctional catalases. How hydrogen peroxide (H2O2) reaches the active site and outcompetes water molecules to be able to function at a very high rate is one of the issues examined. Part of the answer is a gate valve system that is instrumental to drive out solvent molecules from the final section of the main channel. A second issue relates to how the enzyme deals with an unproductive reactive compound I (Cpd I) intermediate. Peroxidatic two and one electron donors and the transfer of electrons to the active site from NADPH and other compounds are reviewed. The new ascribed catalase reactions are revised, indicating possible measurement pitfalls. A third issue concerns the heme b to heme d oxidation, why this reaction occurs only in some large-size subunit catalases (LSCs), and the possible role of singlet oxygen in this and other modifications. The formation of a covalent bond between the proximal tyrosine with the vicinal residue is analyzed. The last issue refers to the origin and function of the additional C-terminal domain (TD) of LSCs. The TD has a molecular chaperone activity that is traced to a gene fusion between a Hsp31-type chaperone and a small-size subunit catalase (SSC).

Large-Size Subunit Catalases Are Chimeric Proteins: A H2O2 Selecting Domain with Catalase Activity Fused to a Hsp31-Derived Domain Conferring Protein Stability and Chaperone Activity

Bacterial and fungal large-size subunit catalases (LSCs) are like small-size subunit catalases (SSCs) but have an additional C-terminal domain (CT). The catalytic domain is conserved at both primary sequence and structural levels and its amino acid composition is optimized to select H₂O₂ over water. The CT is structurally conserved, has an amino acid composition similar to very stable proteins, confers high stability to LSCs, and has independent molecular chaperone activity. While heat and denaturing agents increased Neurospora crassa catalase-1 (CAT-1) activity, a CAT-1 version lacking the CT (C63) was no longer activated by these agents. The addition of catalase-3 (CAT-3) CT to the CAT-1 or CAT-3 catalase domains prevented their heat denaturation in vitro. Protein structural alignments indicated CT similarity with members of the DJ-1/PfpI superfamily and the CT dimers present in LSCs constitute a new type of symmetric dimer within this superfamily. However, only the bacterial Hsp31 proteins show sequence similarity to the bacterial and fungal catalase mobile coil (MC) and are phylogenetically related to MC_CT sequences. LSCs might have originated by fusion of SSC and Hsp31 encoding genes during early bacterial diversification, conferring at the same time great stability and molecular chaperone activity to the novel catalases.

Saponins and flavonoids from Bacopa floribunda plant extract exhibit antioxidant and anti-inflammatory effects on amyloid beta 1-42-induced Alzheimer's disease in BALB/c mice

ETHNOPHARMACOLOGICAL RELEVANCE

Bacopa floribunda (BF), a locally available plant has been employed traditionally as memory enhancer in Southwestern, Nigeria. It has been utilized in traditional and Ayurvedic medicine as brain tonic for enhancing memory, anti-aging and forestalling series of psychological disorders. However, there is a dearth of scientific information on the mechanism(s) of action of important phytochemicals from BF extract on dementia.

AIM OF THE STUDY

Alzheimer's disease, the commonest form of dementia has been postulated to triple by 2050 as a result of increase in life expectancy. This study therefore assessed and compared the possible mechanism(s) of action of flavonoids and saponins from BF on Amyloid beta (Aβ1-42)-induced dementia in male BALB/c mice.

MATERIALS AND METHODS

Eighty (80) healthy BALB/c mice divided into 10 groups (n = 8) were given a single bilateral ICV injection of Aβ1-42 or normal saline. Graded doses of Saponins and flavonoids (50, 100 and 200 mg/kg) were used as treatment for 21 days. Hippocampal homogenates were assayed for the levels of antioxidants, oxidative stress and neuroinflammatory markers. In vitro antioxidant activity of flavonoids and saponins were equally assessed using standard procedures. The extent of microglial activation was quantified through immunohistochemistry procedure.

RESULTS

Aβ1-42 successfully caused a spike in hippocampal levels of MDA, IL1β, TNF-α including MPO levels and invariably decreased antioxidant activities. Likewise an increase in reactive microglia (microgliosis) was observed. However, crude saponins and flavonoids from BF were able to suppress microgliosis, oxidative stress and neuroinflammation induced by Aβ1- 42 and were observed to be more effective at higher doses of saponins (100 mg/kg and 200 mg/kg) and flavonoid (100 mg/kg).

CONCLUSIONS

Phytochemicals from BF efficiently exhibited dose dependent alleviation of some symptoms associated with Alzheimer's disease.

Basidiomycota Fungi and ROS: Genomic Perspective on Key Enzymes Involved in Generation and Mitigation of Reactive Oxygen Species

Our review includes a genomic survey of a multitude of reactive oxygen species (ROS) related intra- and extracellular enzymes and proteins among fungi of Basidiomycota, following their taxonomic classification within the systematic classes and orders, and focusing on different fungal lifestyles (saprobic, symbiotic, pathogenic). Intra- and extracellular ROS metabolism-involved enzymes (49 different protein families, summing 4170 protein models) were searched as protein encoding genes among 63 genomes selected according to current taxonomy. Extracellular and intracellular ROS metabolism and mechanisms in Basidiomycota are illustrated in detail. In brief, it may be concluded that differences between the set of extracellular enzymes activated by ROS, especially by H2O2, and involved in generation of H2O2, follow the differences in fungal lifestyles. The wood and plant biomass degrading white-rot fungi and the litter-decomposing species of Agaricomycetes contain the highest counts for genes encoding various extracellular peroxidases, mono- and peroxygenases, and oxidases. These findings further confirm the necessity of the multigene families of various extracellular oxidoreductases for efficient and complete degradation of wood lignocelluloses by fungi. High variations in the sizes of the extracellular ROS-involved gene families were found, however, among species with mycorrhizal symbiotic lifestyle. In addition, there are some differences among the sets of intracellular thiol-mediation involving proteins, and existence of enzyme mechanisms for quenching of intracellular H2O2 and ROS. In animal- and plant-pathogenic species, extracellular ROS enzymes are absent or rare. In these fungi, intracellular peroxidases are seemingly in minor role than in the independent saprobic, filamentous species of Basidiomycota. Noteworthy is that our genomic survey and review of the literature point to that there are differences both in generation of extracellular ROS as well as in mechanisms of response to oxidative stress and mitigation of ROS between fungi of Basidiomycota and Ascomycota.

Secretome analysis identified extracellular superoxide dismutase and catalase of Macrophomina phaseolina

Macrophomina phaseolina, a necrotrophic fungal pathogen is known to cause charcoal rot disease in food crops, pulse crops, oil crops and cotton and fibre crops. Necrotrophic fungi survive on dead plant tissue. It is well known that reactive oxygen species (ROS) are produced by the host plant during plant-pathogen interaction. However, it is still unclear how M. phaseolina can overcome the ROS-induced cellular damage. To mimic the invasion of M. phaseolina inside the plant cell wall, we developed solid substrate fermentation where M. phaseolina spore suspension was inoculated on a wheat bran bed and incubated for vegetative growth. To analyse the secretome of M. phaseolina after different day interval, its secretory material was collected and concentrated. Both superoxide dismutase (SOD) and catalase were detected in the secretome by zymogram. The presence of SOD and catalase was further confirmed by liquid chromatography based mass spectrometry. The physicochemical properties of M. phaseolina catalase in terms of stability towards pH, temperature, metal ions and chaotropic agent and inhibitors indicated its fitness at different environmental conditions. Apart from the production of catalase in SSF, the studies on this particular microorganism may also have significance in necrotrophic fungal pathogen and their susceptible host plant interaction.

Probing the role of Val228 on the catalytic activity of Scytalidium catalase

Scytalidium catalase is a homotetramer including heme d in each subunit. Its primary function is the dismutation of H₂O₂ to water and oxygen, but it is also able to oxidase various small organic compounds including catechol and phenol. The crystal structure of Scytalidium catalase reveals the presence of three linked channels providing access to the exterior like other catalases reported so far. The function of these channels has been extensively studied, revealing the possible routes for substrate flow and product release. In this report, we have focussed on the semi-conserved residue Val228, located near to the vinyl groups of the heme at the opening of the lateral channel. Its replacement with Ala, Ser, Gly, Cys, Phe and Ile were tested. We observed a significant decrease in catalytic efficiency in all mutants with the exception of a remarkable increase in oxidase activity when Val228 was mutated to either Ala, Gly or Ser. The reduced catalytic efficiencies are characterized in terms of the restriction of hydrogen peroxide as electron acceptor in the active centre resulting from the opening of lateral channel inlet by introducing the smaller side chain residues. On the other hand, the increased oxidase activity is explained by allowing the suitable electron donor to approach more closely to the heme. The crystal structures of V228C and V228I were determined at 1.41 and 1.47 Å resolution, respectively. The lateral channels of the V228C and V228I presented a broadly identical chain of arranged waters to that observed for wild-type enzyme.

iTRAQ-based comparative proteome analyses of different growth stages revealing the regulatory role of reactive oxygen species in the fruiting body development of Ophiocordyceps sinensis

In this study, using an isobaric tags for relative and absolute quantitation (iTRAQ ) approach coupled with LC-MS / MS and bioinformatics, the proteomes were analyzed for the crucial three stages covering the fruiting body development of Ophiocordyceps sinensis, including sclerotium (ST), primordium (PR) and mature fruiting body (MF), with a focus on fruiting body development-related proteins and the potential mechanisms of the development. A total of 1,875 proteins were identified. Principal Component Analysis (PCA) demonstrated that the protein patterns between PR and MF were more similar than ST. Differentially accumulated proteins (DAPs) analysis showed that there were 510, 173 and 514 DAPs in the comparisons of ST vs. PR, PR vs. MF and ST vs. MF, respectively. A total of 62 shared DAPs were identified and primarily enriched in proteins related to ‘carbon transport and mechanism’, ‘the response to oxidative stress’, ‘antioxidative activity’ and ‘translation’. KEGG and GO databases showed that the DAPs were enriched in terms of ‘primary metabolisms (amino acid/fatty acid/energy metabolism)’, ‘the response to oxidative stress’ and ‘peroxidase’. Furthermore, 34 DAPs involved in reactive oxygen species (ROS) metabolism were identified and clustered across the three stages using hierarchical clustering implemented in hCluster R package . It was suggested that their roles and the underlying mechanisms may be stage-specific. ROS may play a role in fungal pathogenicity in ST, the fruit-body initiation in PR, sexual reproduction and highland adaptation in MF. Crucial ROS-related proteins were identified, such as superoxide dismutase (SOD, T5A6F1), Nor-1 (T5AFX3), electron transport protein (T5AHD1), histidine phosphotransferase (HPt, T5A9Z5) and Glutathione peroxidase (T5A9V1). Besides, the accumulation of ROS at the three stages were assayed using 2,7-dichlorofuorescin diacetate (DCFH-DA) stanning. A much stronger ROS accumulation was detected at the stage MF, compared to the stages of PR and ST. Sections of ST and fruit-body part of MF were stained by DCFH-DA and observed under the fluorescencemicroscope, showing ROS was distributed within the conidiospore and ascus. Besides, SOD activity increased across the three stages, while CAT activity has a strong increasement in MF compared to the stages of ST and PR. It was suggested that ROS may act in gradient-dependent manner to regulate the fruiting body development. The coding region sequences of six DAPs were analyzed at mRNA level by quantitative real-time PCR (qRT-PCR). The results support the result of DAPs analysis and the proteome sequencing data. Our findings offer the perspective of proteome to understand the biology of fruiting body development and highland adaptation in O. sinensis, which would inform the big industry of this valuable fungus.

On the Anti-Cancer Effect of Cold Atmospheric Plasma and the Possible Role of Catalase-Dependent Apoptotic Pathways

Cold atmospheric plasma (CAP) is a promising new agent for (selective) cancer treatment, but the underlying cause of the anti-cancer effect of CAP is not well understood yet. Among different theories and observations, one theory in particular has been postulated in great detail and consists of a very complex network of reactions that are claimed to account for the anti-cancer effect of CAP. Here, the key concept is a reactivation of two specific apoptotic cell signaling pathways through catalase inactivation caused by CAP. Thus, it is postulated that the anti-cancer effect of CAP is due to its ability to inactivate catalase, either directly or indirectly. A theoretical investigation of the proposed theory, especially the role of catalase inactivation, can contribute to the understanding of the underlying cause of the anti-cancer effect of CAP. In the present study, we develop a mathematical model to analyze the proposed catalase-dependent anti-cancer effect of CAP. Our results show that a catalase-dependent reactivation of the two apoptotic pathways of interest is unlikely to contribute to the observed anti-cancer effect of CAP. Thus, we believe that other theories of the underlying cause should be considered and evaluated to gain knowledge about the principles of CAP-induced cancer cell death.

Chaperone activity of large-size subunit catalases

Large-size subunit catalases (LSCs) have a C-terminal domain that is structurally similar to DJ-1 and Hsp31 proteins, which have well documented molecular chaperone activity. Like chaperones, LSCs are abundant proteins that are induced under stress conditions and during cell differentiation in different microorganisms. Here we document that the C-terminal domain of LSCs assist other proteins to preserve their active conformation. Heat, urea, or H₂O₂ denaturation of alcohol dehydrogenase was prevented by LSCs or the C-terminal domain of Catalase-3 (TDC3); in contrast, small-size subunit catalases (SSCs) or LSCs without the C-terminal domain (C3^ΔTD or C63) did not have this effect. Similar results were obtained if the alcohol dehydrogenase was previously denatured by heat and then the different catalases or truncated enzymes were added. The TDC3 also protected both the C3^ΔTD and the bovine liver catalase from heat denaturation. The chaperone activity of CAT-3 or the TDC3 increased survival of E. coli under different stress conditions whereas the C3^ΔTD did not. It is concluded that the C-terminal domain of LSCs has a chaperone activity that is instrumental for cellular resistance to stress conditions, such as oxidative stress that leads to cell differentiation in filamentous fungi.

Thermodynamics and kinetics of thermal deactivation of catalase Aspergillus niger

The thermal stability of enzyme-based biosensors is crucial in economic feasibility. In this study, thermal deactivation profiles of catalase Aspergillus niger were obtained at different temperatures in the range of 35°C to 70°C. It has been shown that the thermal deactivation of catalase Aspergillus niger follows the first-order model. The half-life time t 1/2 of catalase Aspergillus niger at pH 7.0 and the temperature of 35°C and 70°C were 197 h and 1.3 h respectively. Additionally, t 1/2 of catalase Aspergillus niger at the temperature of 5°C was calculated 58 months. Thermodynamic parameters the change in enthalpy ΔH*, the change in entropy ΔS* and the change Gibbs free energy ΔG* for the deactivation of catalase at different temperatures in the range of 35°C to 70°C were estimated. Catalase Aspergillus niger is predisposed to be used in biosensors by thermodynamics parameters obtained.

Purification and characterization of Terfezia claveryi TcCAT-1, a desert truffle catalase upregulated in mycorrhizal symbiosis

Terfezia claveryi Chatin is a mycorrhizal fungus that forms ectendomycorrhizal associations with plants of Helianthemum genus. Its appreciated edibility and drought resistance make this fungus a potential alternative crop in arid and semiarid areas of the Mediterranean region. In order to increase the knowledge about the biology of this fungus in terms of mycorrhiza formation and response to drought stress, a catalase from T. claveryi (TcCAT-1) has been purified to apparent homogeneity and biochemically characterized; in addition, the expression pattern of this enzyme during different stages of T. claveryi biological cycle and under drought stress conditions are reported. The results obtained, together with the phylogenetic analysis and homology modeling, indicate that TcCAT-1 is a homotetramer large subunit size monofunctional-heme catalase belonging to Clade 2. The highest expression of this enzyme occurs in mature mycorrhiza, revealing a possible role in mycorrhiza colonization, but it is not upregulated under drought stress. However, the H2O2 content of mycorrhizal plants submitted to drought stress is lower than in well watered treatments, suggesting that mycorrhization improves the plant's oxidative stress response, although not via TcCAT-1 upregulation.

The role of catalases in the prevention/promotion of oxidative stress

Catalases, heme enzymes which catalyze decomposition of hydrogen peroxide to water and molecular oxygen, are important members of the antioxidant defense system of cells of almost all aerobic organisms. However, recent studies suggest that catalase may be involved in various other processes in the cell. The paper provides a review of reactions of catalases with their main substrate, hydrogen peroxide, and with oxidizing species such as hydroxyl radical, superoxide, nitric oxide, peroxynitrite, hypochlorous acid, and singlet oxygen. A number of these individuals are formed under oxidative eustress (good stress) as well as distress (bad stress), while others only under conditions of oxidative distress. Potential biological significance of the reactions of mammalian as well as bacterial catalases with oxidizing species is discussed. The majority of these reactions inhibit catalase. Authors emphasize that catalase inhibition, which may lead to significant increase of the local concentration of hydrogen peroxide, may be detrimental to the neighboring tissues, but in some pathological states (e.g. the defense directed against pathogenic bacteria rich in catalase, or induction of apoptosis of cancer cells which possess membrane-associated catalase) it may be beneficial for the host organism.

Catalase-1 (CAT-1) and nucleoside diphosphate kinase-1 (NDK-1) play an important role in protecting conidial viability under light stress in Neurospora crassa

Recently we reported that Catalase-1 (CAT-1) played an important role in protecting conidial viability in Neurospora crassa, and interacted with a light signal transducer, nucleoside diphosphate kinase-1 (NDK-1). To disclose the functional interaction between CAT-1 and NDK-1 at the genetic level, we created CAT-1 and NDK-1 double mutants, cat-1;ndk-1-1 and cat-1;ndk-1-2, by crossing single mutants of cat-1 ( RIP ) and ndk-1 ( P72H ) previously isolated in our laboratory. The double mutant strains grew normally, but showed increased CAT-2 activity. In cat-1 ( RIP ), NDK activity was increased when dCDP was used as a substrate. ndk-1 ( P72H ), cat-1;ndk-1-1, and cat-1;ndk-1-2 were more sensitive to riboflavin than the wild type and cat-1 ( RIP ) under strong light (100 microE m(-2) s(-1)). The pull-down experiment suggests that His-tagged NDK-1 is bound to [(32)P]NADH. However, his-tagged NDK-1(P72H) was not bound to [(32)P]NADH. The double mutants showed much lower conidial viability and lost all conidial germination ability much more rapidly than cat-1 ( RIP ), when they were cultured under continuous light for more than 2 weeks. These results indicate that the interaction of CAT-1 with NDK-1 plays an important role in supporting the survival of conidia under oxidative and light-induced stress including singlet oxygen, and confirm our former conclusion that reactive oxygen species play an important role in light signal transduction via NDK-1 at the genetic level.

Non-oxygen-forming pathways of hydrogen peroxide degradation by bovine liver catalase at low hydrogen peroxide fluxes

Heme catalases are considered to degrade two molecules of H(2)O(2) to two molecules of H(2)O and one molecule of O(2) employing the catalatic cycle. We here studied the catalytic behaviour of bovine liver catalase at low fluxes of H(2)O(2) (relative to catalase concentration), adjusted by H(2)O(2)-generating systems. At a ratio of a H(2)O(2) flux (given in microM/min(- 1)) to catalase concentration (given in microM) of 10 min(- 1) and above, H(2)O(2) degradation occurred via the catalatic cycle. At lower ratios, however, H(2)O(2) degradation proceeded with increasingly diminished production of O(2). At a ratio of 1 min(- 1), O(2) formation could no longer be observed, although the enzyme still degraded H(2)O(2). These results strongly suggest that at low physiological H(2)O(2) fluxes H(2)O(2) is preferentially metabolised reductively to H(2)O, without release of O(2). The pathways involved in the reductive metabolism of H(2)O(2) are presumably those previously reported as inactivation and reactivation pathways. They start from compound I and are operative at low and high H(2)O(2) fluxes but kinetically outcompete the reaction of compound I with H(2)O(2) at low H(2)O(2) production rates. In the absence of NADPH, the reducing equivalents for the reductive metabolism of H(2)O(2) are most likely provided by the protein moiety of the enzyme. In the presence of NADPH, they are at least in part provided by the coenzyme.

UVA-induced modification of catalase charge properties in the epidermis is correlated with the skin phototype

The harmful effects of UVA radiation (320-400 nm) on the skin have been related to the generation of reactive oxygen species. Pheomelanin, the pigment characteristic of fair-skinned individuals, amplifies these effects. In vitro, in the presence of photosensitizing agents, UVA light produces singlet oxygen, which reacts with several targets. We have investigated a possible correlation between melanin-type and the antioxidant defense system after UV, focusing on the activities of superoxide dismutase and catalase, which correlated with the phototype of epidermal reconstructs. UVA was more effective than UVB in damaging these enzymatic activities, especially catalase. Furthermore, UVA irradiation induced a free-radical-mediated damage in the cells, leading to an oxidation of cell proteins. On catalase, synthetic pheomelanin amplified this effect on specific targets, such as residues of tryptophan and methionine. UVA irradiation of low phototype reconstructed epidermis and of U937 through synthetic pheomelanin induced a modification in the electrophoretic properties of native catalase, which was counteracted by histidine, a quencher of singlet oxygen. These results demonstrate that pheomelanin could act as a photosensitizing agent, following UVA irradiation, inducing charge modifications of native catalase, by a mechanism involving singlet oxygen or its downstream products.