Purification, biochemical characterization, and implications of an alkali-tolerant catalase from the spacecraft-associated and oxidation-resistant Acinetobacter gyllenbergii 2P01AA

Structure and functional properties of the cold-adapted catalase from Acinetobacter sp. Ver3 native to the Atacama plateau in northern Argentina

Heme catalases remove hydrogen peroxide by catalyzing its dismutation into water and molecular oxygen, thereby protecting the cell from oxidative damage. The Atacama plateau in northern Argentina, located 4000 m above sea level, is a desert area characterized by extreme UV radiation, high salinity and a large temperature variation between day and night. Here, the heme catalase KatE1 from an Atacama Acinetobacter sp. isolate was cloned, expressed and purified, with the aim of investigating its extremophilic properties. Kinetic and stability assays indicate that KatE1 is maximally active at 50°C in alkaline media, with a nearly unchanged specific activity between 0°C and 40°C in the pH range 5.5-11.0. In addition, its three-dimensional crystallographic structure was solved, revealing minimal structural differences compared with its mesophilic and thermophilic analogues, except for a conserved methionine residue on the distal heme side, which is proposed to comprise a molecular adaptation to oxidative damage.

Simple kinetics, assay, and trends for soil microbial catalases

In this report, we expand upon the enzymology and ecology of soil catalases through development and application of a simple kinetic model and field-amenable assay based upon volume displacement. Through this approach, we (A) directly relate apparent Michaelis-Menten terms to the catalase reaction mechanism, (B) obtain upper estimates of the intrinsic rate constants for the catalase community (k₃^'), along with moles of catalase per 16S rRNA gene copy number, (C) utilize catalase specific activities (SAs) to obtain biomass estimates of soil and permafrost communities (LOD, ~10⁴ copy number gdw^-1), and (D) relate kinetic trends to changes in bacterial community structure. In addition, this novel kinetic approach simultaneously incorporates barometric adjustments to afford comparisons across field measurements. As per our model, and when compared to garden soils, biological soil crusts exhibited ~2-fold lower values for k₃^', ≥10⁵-fold higher catalase moles per biomass (250-1200 zmol copy number^-1), and ~10⁴-fold higher SAs per biomass (74-230 fkat copy number^-1); whereas the highest SAs were obtained from permafrost and high-elevation soil communities (5900-6700 fkat copy number^-1). In sum, the total trends suggest that microbial communities which experience higher degrees of native oxidative stress possess higher basal intracellular catalase concentrations and SAs per biomass.

Catalases of the polyextremophylic Andean isolate Acinetobacter sp. Ver 3 confer adaptive response to H2 O2 and UV radiation

The polyextremophilic strain Acinetobacter sp. Ver3 isolated from high-altitude Andean lakes exhibits elevated tolerance to UV-B radiation and to pro-oxidants, a feature that has been correlated to its unusually high catalase activity. The Ver3 genome sequence analysis revealed the presence of two genes coding for monofunctional catalases: ^AV3 KatE1 and ^AV3 KatE2, the latter harboring an N-terminal signal peptide. We show herein that ^AV3 KatE1 displays one of the highest catalytic activities reported so far and is constitutively expressed at relatively high amounts in the cytosol, acting as the main protecting catalase against H₂ O₂ and UV-B radiation. The second catalase, ^AV3 KatE2, is a periplasmic enzyme strongly induced by both peroxide and UV, conferring supplementary protection against pro-oxidants. The N-terminal signal present in ^AV3 KatE2 was required not only for transport to the periplasm via the twin-arginine translocation pathway, but also for proper folding and subsequent catalytic activity. The analysis of catalase distribution among 114 Acinetobacter complete genomes revealed a great variability in the catalase classes, with A. baumannii clinical isolates exhibiting higher numbers of isoenzymes and the most variable profiles.

High level extracellular production of a recombinant alkaline catalase in E. coli BL21 under ethanol stress and its application in hydrogen peroxide removal after cotton fabrics bleaching

The effects of induction parameters, osmolytes and ethanol stress on the productivity of the recombinant alkaline catalase (KatA) in Escherichia coli BL21 (pET26b-KatA) were investigated. The yield of soluble KatA was significantly enhanced by 2% ethanol stress. And a certain amount of Triton X-100 supplementation could markedly improved extracellular ratio of KatA. A total soluble catalase activity of 78,762U/mL with the extracellular ratio of 92.5% was achieved by fed-batch fermentation in a 10L fermentor, which was the highest yield so far. The purified KatA showed high stability at 50°C and pH 6-10. Application of KatA for elimination of H2O2 after cotton fabrics bleaching led to less consumption of water, steam and electric power by 25%, 12% and 16.7% respectively without productivity and quality losing of cotton fabrics. Thus, the recombinant KatA is a promising candidate for industrial production and applications.