Characterization of catalase from psychrotolerant Psychrobacter piscatorii T-3 exhibiting high catalase activity

Relationship Between Main Channel Structure of Catalases and the Evolutionary Direction in Cold-Adapted Hydrogen Peroxide-Tolerant Exiguobacteium and Psychrobacter

Catalase has crucial role in adaptive response to H₂O₂. Main channel structure responsible for substrate selectivity was estimated to understand the relationship between the evolutionary direction of catalases from Exiguobacterium oxidotolerans and Psychrobacter piscatorii which survive in cold and high concentration of hydrogen peroxide, and their catalytic property. E. oxidotolerans catalase (EKTA) exhibited a higher ratio of compound I formation rate using peracetic acid (a substrate lager than H₂O₂)/catalase activity using H₂O₂ as the substrate than P. piscatori catalase (PKTA). It was considered that the ratio was attributed to the size of the amino acid residues locating at the bottle neck structure in the main channel. The differences in the ratio of the compound I formation rate with peracetic acid to catalase activity with H₂O₂ between the deeper branches in the phylogenetic tree in both EKTA and PKTA were large. This indicates that catalases from the hydrogen peroxide-tolerant bacteria have evolved in different directions, exhibiting effective catalytic activity and allowing broader substrates size or H₂O₂-specific substrate acceptability in EKTA and PKTA, respectively. It is considered that the main channel structure reflected the difference in the evolutionary direction of clade 1 and clade 3 catalases.

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.

Applications of Microbial Enzymes in Food Industry

The use of enzymes or microorganisms in food preparations is an age-old process. With the advancement of technology, novel enzymes with wide range of applications and specificity have been developed and new application areas are still being explored. Microorganisms such as bacteria, yeast and fungi and their enzymes are widely used in several food preparations for improving the taste and texture and they offer huge economic benefits to industries. Microbial enzymes are the preferred source to plants or animals due to several advantages such as easy, cost-effective and consistent production. The present review discusses the recent advancement in enzyme technology for food industries. A comprehensive list of enzymes used in food processing, the microbial source of these enzymes and the wide range of their application are discussed.

Molecular Insights into the Potential Toxicological Interaction of 2-Mercaptothiazoline with the Antioxidant Enzyme-Catalase

2-mercaptothiazoline (2-MT) is widely used in many industrial fields, but its residue is potentially harmful to the environment. In this study, to evaluate the biological toxicity of 2-MT at protein level, the interaction between 2-MT and the pivotal antioxidant enzyme—catalase (CAT) was investigated using multiple spectroscopic techniques and molecular modeling. The results indicated that the CAT fluorescence quenching caused by 2-MT should be dominated by a static quenching mechanism through formation of a 2-MT/CAT complex. Furthermore, the identifications of the binding constant, binding forces, and the number of binding sites demonstrated that 2-MT could spontaneously interact with CAT at one binding site mainly via Van der Waals’ forces and hydrogen bonding. Based on the molecular docking simulation and conformation dynamic characterization, it was found that 2-MT could bind into the junctional region of CAT subdomains and that the binding site was close to enzyme active sites, which induced secondary structural and micro-environmental changes in CAT. The experiments on 2-MT toxicity verified that 2-MT significantly inhibited CAT activity via its molecular interaction, where 2-MT concentration and exposure time both affected the inhibitory action. Therefore, the present investigation provides useful information for understanding the toxicological mechanism of 2-MT at the molecular level.

Cloning, Expression, and Characterization of a Novel Thermophilic Monofunctional Catalase from Geobacillus sp. CHB1

Catalases are widely used in many scientific areas. A catalase gene (Kat) from Geobacillus sp. CHB1 encoding a monofunctional catalase was cloned and recombinant expressed in Escherichia coli (E. coli), which was the first time to clone and express this type of catalase of genus Geobacillus strains as far as we know. This Kat gene was 1,467 bp in length and encoded a catalase with 488 amino acid residuals, which is only 81% similar to the previously studied Bacillus sp. catalase in terms of amino acid sequence. Recombinant catalase was highly soluble in E. coli and made up 30% of the total E. coli protein. Fermentation broth of the recombinant E. coli showed a high catalase activity level up to 35,831 U/mL which was only lower than recombinant Bacillus sp. WSHDZ-01 among the reported catalase production strains. The purified recombinant catalase had a specific activity of 40,526 U/mg and K m of 51.1 mM. The optimal reaction temperature of this recombinant enzyme was 60°C to 70°C, and it exhibited high activity over a wide range of reaction temperatures, ranging from 10°C to 90°C. The enzyme retained 94.7% of its residual activity after incubation at 60°C for 1 hour. High yield and excellent thermophilic properties are valuable features for this catalase in industrial applications.

Analysis of microbiota on abalone (Haliotis discus hannai) in South Korea for improved product management

Abalone is a popular seafood in South Korea; however, because it contains various microorganisms, its ingestion can cause food poisoning. Therefore, analysis of the microbiota on abalone can improve understanding of outbreaks and causes of food poisoning and help to better manage seafood products. In this study, we collected a total of 40 abalones from four different regions in March and July, which are known as the maximum abalone production areas in Korea. The microbiota were analyzed using high-throughput sequencing, and bacterial loads on abalone were quantified by real-time PCR. Over 2700 species were detected in the samples, and Alpha- and Gammaproteobacteria were the predominant classes. The differences in microbiota among regions and at each sampling time were also investigated. Although Psychrobacter was the dominant genus detected on abalone in both March and July, the species compositions were different between the two sampling times. Five potential pathogens (Lactococcus garvieae, Yersinia kristensenii, Staphylococcus saprophyticus, Staphylococcus warneri, and Staphylococcus epidermidis) were detected among the abalone microbiota. In addition, we analyzed the influence of Vibrio parahaemolyticus infection on shifts in abalone microbiota during storage at different temperatures. Although the proportion of Vibrio increased over time in infected and non-infected abalone, the shifts of microbiota were more dynamic in infected abalone. These results can be used to better understand the potential of food poisoning caused by abalone consumption and manage abalone products according to the microbiota composition.

Draft Genome Sequence of Psychrobacter piscatorii Strain LQ58, a Psychrotolerant Bacterium Isolated from a Deep-Sea Hydrothermal Vent

Here, we report the 3.1-Mb draft genome sequence of Psychrobacter piscatorii strain LQ58, isolated from a deep-sea hydrothermal vent on the East Pacific Rise. The sequence will provide further insight into the environmental adaptation of psychrotolerant bacteria and the development of novel cold-active enzymes for industrial application.

Growth-dependent catalase localization in Exiguobacterium oxidotolerans T-2-2T reflected by catalase activity of cells

A psychrotolerant and H₂O₂-resistant bacterium, Exiguobacterium oxidotolerans T-2-2^T, exhibits extraordinary H₂O₂ resistance and produces catalase not only intracellularly but also extracellularly. The intracellular and extracellular catalases exhibited the same enzymatic characteristics, that is, they exhibited the temperature-dependent activity characteristic of a cold-adapted enzyme, their heat stabilities were similar to those of mesophilic enzymes and very high catalytic intensity. In addition, catalase gene analysis indicated that the bacterium possessed the sole clade 1 catalase gene corresponding to intracellular catalase. Hence, intracellular catalase is secreted into the extracellular space. In addition to intracellular and extracellular catalases, the inner circumference of the cells showed the localization of catalase in the mid-stationary growth phase, which was observed by immunoelectron microscopy using an antibody against the intracellular catalase of the strain. The cells demonstrated higher catalase activity in the mid-stationary growth phase than in the exponential growth phase. The catalase localized in the inner circumference can be dissociated by treatment with Tween 60. Thus, the localized catalase is not tightly bound to the inner circumference of the cells and may play a role in the oxidative defense of the cells under low metabolic state.