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The reactivity of purified catalase from Exiguobacterium oxidotolerans (EKTA catalase) and the three-dimensional structure of this enzyme refined to a 2.4 Angstrom resolution are reported. The results indicate that the size of the bottleneck in the main channel in catalase is an important factor in defining the rate of compound reactive intermediates formation corresponding to the molecular size of the substrates.

Results show that the purified catalase from the Vibrio rumoiensis S-1(sup)T is a 230 kilodalton molecular mass enzyme exhibiting four identical subunits. Data also indicate that the unique properties of the enzyme are consistent with bacterium's exposure to an environment of hydrogen peroxide.

A new strain of the facultatively psychrophilic bacterium Vibrio rumoiensis with high catalase activity has been studied. The strain, called S-1, was isolated from the drain pool of a fish procesing plant which uses H2O2 as the bleaching and microbiocidal agent. The gel electrophoresis of the cell extract revealed tha S-1 has only one kind of catalase. Its catalase activity was one or two orders of magnitude higher than those of C. glutamicum, S. aureus, P. fluorescens and five other species tested. The optimum temperature for catalase activity was 30 degrees C which was 20 degrees lower than that for bovine catalase.

The extraordinarily high level of H2O2 tolerance of Vibrio rumoiensis strain S-1T when compared with the tolerance levels of strain S-4, a probable catalase-deficient derivative of strain S-1T, was demonstrated by the introduction of 0–100 mM H2O2 during the mid-exponential growth phase. The contribution of catalase to the H2O2 tolerance was also demonstrated by comparing the catalase-deficient mutant Escherichia coli strain UM2 with a UM2 strain, harboring the plasmid pBSsa1, which carried the strain S-1T catalase gene vktA. The decomposition rates of 23–25 mM H2O2 that was introduced in the culture fluids of strain S-1T and E. coli UM2 harboring pBSsa1 corresponded to the calatase activities of the cells by spectrophotometric measurements. The presence of cell surface catalase was observed by immunoelectron microscopy, using an antibody for intracellular catalase in strain S-1T. The high level of H2O2 tolerance of strain S-1T was attributable to the catalase activity of the cells. Cell surface catalase is considered to contribute to the catalase activity of strain S-1T cells. [Copyright &y& Elsevier]

Arabinogalactan proteins (AGPs) are very large proteoglycans thought to have more of a signaling than a structural role when secreted into the plant cell wall. AGPs are also the first known family of abundant plant proteins synthesized with glycosylphosphatidylinositol(GPI) anchors. Nascent cellular Arabidopsis AGPs, still bearing an intact GPI anchor, and AGPs copiously discharged into the culture medium after phospholipase-cleavage of their anchor were each represented by more than 15 seemingly homologous molecular species of increasing size. In washed cells 3H-ethanolamine was slowly incorporated into each AGP’s GPI anchor via phosphatidylethanolamine. Pulse labeling of AGPs by 3H-acetate and by 3H-galactose was much more rapid, allowing labeled AGP detection in the growth medium within 1 h. HPLC analysis of the radiolabel distribution in AGPs secreted within 1–8 h revealed a sharp preference for the larger molecular species. After several hours a population of smaller radioactive AGP species began to appear in the medium. Following certain manipulations of the cells newly secreted AGP species measured by HPLC on a relative mass basis formed a pattern surprisingly different from the radioactivity pattern, although larger species still dominated. Thus Arabidopsis cells appear capable of releasing higher mass AGP species apparently stored in cell wall sites along with a unique mixture of freshly synthesized AGPs in combinations potentially active in signaling. [Copyright &y& Elsevier]

A soluble class I cytochrome c of an alkaliphile was purified and characterized, and its primary structure was determined. This is the first example of a soluble class I cytochrome c in alkaliphiles. Cells the alkaliphilic gram-negative bacterium Pseudomonas alcaliphila AL15-21T grown at pH 10 had a soluble cytochrome c content that was more than twofold that of strain AL15-21T cells grown at pH 7 under air-limited conditions. Cytochrome c-552, a soluble cytochrome c with a low molecular weight, was purified from strain AL15-21T cells grown at pH 10 under air-limited conditions. Cytochrome c-552 had a molecular mass of 7.5 kDa and exhibited an almost fully reduced state in the resting form, which exhibited absorption maxima at wavelengths of 552, 523 and 417 nm. In the oxidized state, it exhibited an absorption maximum at 412 nm when it was oxidized by ferricyanide, its isoelectric point (pI) was 4.3 and it contained one heme c as a prosthetic group. Cytochrome c-552 was autoreduced at pH 10, and the autoreduction was reproducible. On the other hand, the autoreduction of cytochrome c-552 was not observed at pH 7.0. When pH was increased from 7.0 to 8.3, its midpoint redox potentials (E m values) increased from +228 mV to +276 mV as determined by redox titrations, and from +217 mV to +275 mV as determined by cyclic voltammetric measurements. The amino acid sequence deduced by cytochrome c-552 gene analysis revealed that the sequence consists of 96 residues, including 19 residues as an amino-terminal signal peptide. A phylogenetic tree based on amino acid sequence indicated that the protein belongs to group 4, cytochrome c 5 in class I cytochrome c. [Copyright &y& Elsevier]

Background: Exercise, especially high-intensity interval training (HIIT), can increase mitochondrial respiratory capacity and enhance muscular endurance, but its systemic burden makes it difficult to safely and continuously prescribe for patients with chronic kidney disease (CKD)-related cachexia who are in poor general condition. In this study, we examined whether HIIT using electrical stimulation (ES), which does not require whole-body exercise, improves muscle endurance in the skeletal muscle of 5/6 nephrectomized rats, a widely used animal model for CKD-related cachexia., Methods: Male Wistar rats (10 weeks old) were randomly assigned to a group of sham-operated (Sham) rats and a group of 5/6 nephrectomy (Nx) rats. HIIT was performed on plantar flexor muscles in vivo with supramaximal ES every other day for 4 weeks to assess muscle endurance, myosin heavy-chain isoforms, and mitochondrial respiratory function in Nx rats. A single session was also performed to identify upstream signaling pathways altered by HIIT using ES., Results: In the non-trained plantar flexor muscles from Nx rats, the muscle endurance was significantly lower than that in plantar flexor muscles from Sham rats. The proportion of myosin heavy chain IIa/x, mitochondrial content, mitochondrial respiratory capacity, and formation of mitochondrial respiratory supercomplexes in the plantaris muscle were also significantly decreased in the non-trained plantar flexor muscles from Nx rats than compared to those in plantar flexor muscles from Sham rats. Treatment with HIIT using ES for Nx rats significantly improved these molecular and functional changes to the same degrees as those in Sham rats. Furthermore, a single session of HIIT with ES significantly increased the phosphorylation levels of AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK), pathways that are essential for mitochondrial activation signaling by exercise, in the plantar muscles of both Nx and Sham rats., Conclusion: The findings suggest that HIIT using ES ameliorates muscle fatigue in Nx rats via restoration of mitochondrial respiratory dysfunction with activation of AMPK and p38 MAPK signaling. Our ES-based HIIT protocol can be performed without placing a burden on the whole body and be a promising intervention that is implemented even in conditions of reduced general performance status such as CKD-related cachexia., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Fusagawa, Sato, Yamada, Naito, Tokuda, Yamauchi, Ichise, Ogawa, Karaushi, Teramoto and Tohse.)