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Laminarinase, an enzyme with a specific affinity for laminarin—a complex polysaccharide found in the cell walls of brown algae and select marine organisms—was investigated in this study. We cloned and characterized a gene encoding a putative glycoside hydrolase family 16 (GH16) laminarinase derived from the Jermuk hot spring metagenome. The resulting product, named Jermuk-LamM, represents a novel 1,3-β- d -glucanase with 48.1% amino acid sequence similarity to previously characterized GH16 family members catalogued in the NCBI database. To date, this stands as the sole described endo-1,3-β- d -glucanase from the Fidelibacterota phylum, which was recently reclassified from Marinimicrobia . Jermuk-LamM, identified as an acidic laminarinase, exhibits optimal enzymatic activity at pH 5.0 and a temperature of 55 °C, maintaining its function for a duration of at least 7 h. Jermuk-LamM is an enzyme that efficiently hydrolyzes both soluble and insoluble (1,3)-β- d -glucans, as well as (1,3;1,4)-β- d -glucans, with a marked preference for laminarin. This enzymatic activity facilitates the valorization of macroalgal biomass by predominantly producing monosaccharides and disaccharides. These hydrolysis products can subsequently be converted into energy carriers such as alcohol, methane, and hydrogen. The enzyme’s specific activities, coupled with its resistance to various additives, render Jermuk-LamM a promising candidate for various industrial applications, encompassing the realms of biofuel and pharmaceutical production. Key points • Jermuk hot springs have significant potential as a source of novel enzymes . • Jermuk-LamM has less than 50% amino acid similarity to known enzymes . • It is the first enzyme characterized from the Fidelibacterota phylum .

The development of sustainable and environmentally friendly industrial processes is becoming very crucial and demanding for the rapid implementation of innovative bio-based technologies. Natural extreme environments harbor the potential for discovering and utilizing highly specific and efficient biocatalysts that are adapted to harsh conditions. This review focuses on extremophilic microorganisms and their enzymes (extremozymes) from various hot springs, shallow marine vents, and other geothermal habitats in Europe and the Caucasus region. These hot environments have been partially investigated and analyzed for microbial diversity and enzymology. Hotspots like Iceland, Italy, and the Azores harbor unique microorganisms, including bacteria and archaea. The latest results demonstrate a great potential for the discovery of new microbial species and unique enzymes that can be explored for the development of Circular Bioeconomy.Different screening approaches have been used to discover enzymes that are active at extremes of temperature (up 120 °C), pH (0.1 to 11), high salt concentration (up to 30%) as well as activity in the presence of solvents (up to 99%). The majority of published enzymes were revealed from bacterial or archaeal isolates by traditional activity-based screening techniques. However, the latest developments in molecular biology, bioinformatics, and genomics have revolutionized life science technologies. Post-genomic era has contributed to the discovery of millions of sequences coding for a huge number of biocatalysts. Both strategies, activity- and sequence-based screening approaches, are complementary and contribute to the discovery of unique enzymes that have not been extensively utilized so far.

From a biogas reactor metagenome an ORF (bp_cel9A) encoding a bacterial theme C glycoside hydrolase family 9 (GH9) enzyme was recombinantly produced in E. coli BL21 pQE-80L. BP_Cel9A exhibited ≤ 55% identity to annotated sequences. Subsequently, the enzyme was purified to homogeneity by affinity chromatography. The endo-beta-glucanase BP_Cel9A hydrolyzed the beta-1,3–1,4-linked barley beta-glucan with 24 U/mg at 30 °C and pH 6.0. More than 62% of activity was measured between 10 and 40 °C. Lichenan and xyloglucan were hydrolyzed with 67% and 40% of activity, respectively. The activity towards different substrates varied with different temperatures. However, the enzyme activity on CMC was extremely low (> 1%). In contrast to BP_Cel9A, most GH9 glucanases act preferably on crystalline or soluble cellulose with only side activities towards related substrates. The addition of calcium or magnesium enhanced the activity of BP_Cel9A, especially at higher temperatures. EDTA inhibited the enzyme, whereas EGTA had no effect, suggesting that Mg2+ may adopt the function of Ca2+. BP_Cel9A exhibited a unique substrate spectrum when compared to other GH9 enzymes with great potential for mixed-linked glucan or xyloglucan degrading processes at moderate temperatures.

Laminarinases exhibit potential in a wide range of industrial applications including the production of biofuels and pharmaceuticals. In this study, we present the genetic and biochemical characteristics of FLamA and FLamB, two laminarinases derived from a metagenomic sample from a hot spring in the Azores. Sequence comparison revealed that both genes had high similarities to genes from Fervidobacterium nodosum Rt17-B1. The two proteins showed sequence similarities of 62% to each other and belong to the glycoside hydrolase (GH) family 16. For biochemical characterization, both laminarinases were heterologously produced in Escherichia coli and purified to homogeneity. FLamA and FLamB exhibited similar properties and both showed highest activity towards laminarin at 90 °C and pH 6.5. The two enzymes were thermostable but differed in their half-life at 80 °C with 5 h and 1 h for FLamA and FLamB, respectively. In contrast to other laminarinases, both enzymes prefer β-1,3-glucans and mixed-linked glucans as substrates. However, FLamA and FLamB differ in their catalytic efficiency towards laminarin. Structure predictions were made and showed minor differences particularly in a kink adjacent to the active site cleft. The high specific activities and resistance to elevated temperatures and various additives make both enzymes suitable candidates for application in biomass conversion.

Laminarinase, an enzyme with a specific affinity for laminarin, a complex polysaccharide found in the cell walls of brown algae and select marine organisms, was investigated in this study. We cloned and characterised a gene encoding a putative glycoside hydrolase family 16 (GH16) laminarinase from the Jermuk hot spring metagenome by heterologous expression in Escherichia coli. The resulting product, named Jermuk-LamM, represents a novel endo-1,3-beta-D-glucanase (EC 3.2.1.39) with only 48.1 % amino acid sequence similarity to previously characterised GH16 family members catalogued in the NCBI database. To date, this stands as the sole described endo-1,3-beta-D-glucanase within the Marinimicrobia phylum. Jermuk-LamM, identified as an acidic laminarinase, exhibits robust enzymatic activity at pH 5.0 and a temperature of 55 0C, maintaining its function for a duration of at least 7 hours. Notably, this enzyme effectively catalyses the hydrolysis of both soluble and insoluble (1,3)-beta-D-glucans, as well as (1,3;1,4)-beta-D-glucans, displaying a pronounced preference for laminarin. The specificity of Jermuk-LamM lies in its cleavage of 1,3-beta-D-glucosidic linkages, yielding monosaccharides, disaccharides, and oligosaccharides. These breakdown products hold the potential for conversion into energy carriers, including alcohols, methane, and hydrogen. The enzyme's exceptional specific activities, coupled with its resistance to various additives, render Jermuk-LamM a promising candidate for various industrial applications, encompassing the realms of biofuel and pharmaceutical production.Competing Interest StatementThe authors have declared no competing interest.

Aging induces alterations of tissue protein homoeostasis. To investigate one of the major systems catalysing intracellular protein degradation we have purified 20S proteasomes from rat liver of young (2 months) and aged (23 months) animals and separated them into three subpopulations containing different types of intermediate proteasomes with standard- and immuno-subunits. The smallest subpopulation ΙΙΙ and the major subpopulation Ι comprised proteasomes containing immuno-subunits β1i and β5i beside small amounts of standard-subunits, whereas proteasomes of subpopulation ΙΙ contained only β5i beside standard-subunits. In favour of a relative increase of the major subpopulation Ι, subpopulation ΙΙ and ΙΙΙ were reduced for about 55 % and 80 %, respectively, in aged rats. Furthermore, in all three 20S proteasome subpopulations from aged animals standard-active site subunits were replaced by immuno-subunits. Overall, this transformation resulted in a relative increase of immuno-subunit-containing proteasomes, paralleled by reduced activity towards short fluorogenic peptide substrates. However, depending on the substrate their hydrolysing activity of long polypeptide substrates was significantly higher or unchanged. Furthermore, our data revealed an altered MHC class I antigen-processing efficiency of 20S proteasomes from liver of aged rats. We therefore suggest that the age-related intramolecular alteration of hepatic proteasomes modifies its cleavage preferences without a general decrease of its activity. Such modifications could have implications on protein homeostasis as well as on MHC class I antigen presentation as part of the immunosenescence process.