Functional and structural properties of the homogeneous beta-glycosidase from the extreme thermoacidophilic archaeon sulfolobus solfataricus expressed in Saccharomyces cerevisiae

Glycoside hydrolases from (hyper)thermophilic archaea: structure, function, and applications

(Hyper)thermophilic archaeal glycosidases are enzymes that catalyze the hydrolysis of glycosidic bonds to break down complex sugars and polysaccharides at high temperatures. These enzymes have an unique structure that allows them to remain stable and functional in extreme environments such as hot springs and hydrothermal vents. This review provides an overview of the current knowledge and milestones on the structures and functions of (hyper)thermophilic archaeal glycosidases and their potential applications in various fields. In particular, this review focuses on the structural characteristics of these enzymes and how these features relate to their catalytic activity by discussing different types of (hyper)thermophilic archaeal glycosidases, including β-glucosidases, chitinase, cellulases and α-amylases, describing their molecular structures, active sites, and mechanisms of action, including their role in the hydrolysis of carbohydrates. By providing a comprehensive overview of (hyper)thermophilic archaeal glycosidases, this review aims to stimulate further research into these fascinating enzymes.

Production of Daidzein and Genistein from Seed and Root Extracts of Korean Wild Soybean (Glycine soja) by Thermostable β-Galactosidase from Thermoproteus uzoniensis

Isoflavone glycosides are commonly biotransformed into isoflavone aglycones due to the superior biological activities of the latter. Wild soybeans contain a higher isoflavone content than domesticated soybeans due to their high level of genetic diversity. In this study, we cloned and characterized a thermostable β-galactosidase from the extreme thermophile Thermoproteus uzoniensis for potential application in isoflavone conversion in Korean wild soybeans. The purified recombinant enzyme exhibited a maximum specific activity of 1103 μmol/min/mg at pH 5.0 and 90 °C with a half-life of 46 h and exists as a homodimer of 113 kDa. The enzyme exhibited the highest activity for p-nitrophenyl (pNP)-β-D-galactopyranoside among aryl glycosides and it hydrolyzed isoflavone glycosides in the order genistin > daidzin > ononin > glycitin. The enzyme completely hydrolyzed 2.77 mM daidzin and 3.85 mM genistin in the seed extract of wild soybean after 80 and 70 min with productivities of 1.86 and 3.30 mM/h, respectively, and 9.89 mM daidzin and 1.67 mM genistin in the root extract after 180 and 30 min, with the highest productivities of 3.30 and 3.36 mM/h, respectively, compared to other glycosidases. Our results will contribute to the industrial production of isoflavone aglycone using wild soybean and this is the first report on the enzymatic production of isoflavone aglycones from isoflavone glycosides in wild soybeans.

Overview of strategies for developing high thermostability industrial enzymes: Discovery, mechanism, modification and challenges

Biocatalysts such as enzymes are environmentally friendly and have substrate specificity, which are preferred in the production of various industrial products. However, the strict reaction conditions in industry including high temperature, organic solvents, strong acids and bases and other harsh environments often destabilize enzymes, and thus substantially compromise their catalytic functions, and greatly restrict their applications in food, pharmaceutical, textile, bio-refining and feed industries. Therefore, developing industrial enzymes with high thermostability becomes very important in industry as thermozymes have more advantages under high temperature. Discovering new thermostable enzymes using genome sequencing, metagenomics and sample isolation from extreme environments, or performing molecular modification of the existing enzymes with poor thermostability using emerging protein engineering technology have become an effective means of obtaining thermozymes. Based on the thermozymes as biocatalytic chips in industry, this review systematically analyzes the ways to discover thermostable enzymes from extreme environment, clarifies various interaction forces that will affect thermal stability of enzymes, and proposes different strategies to improve enzymes' thermostability. Furthermore, latest development in the thermal stability modification of industrial enzymes through rational design strategies is comprehensively introduced from structure-activity relationship point of view. Challenges and future research perspectives are put forward as well.

Forty years of study on the thermostable β-glycosidase from S. solfataricus: Production, biochemical characterization and biotechnological applications

The aim of this paper is to make the point on the fortieth years study on the β-glycosidase from Sulfolobus solfataricus. This enzyme represents one of the thermophilic biocatalysts, which is more extensively studied as witnessed by the numerous literature reports available since 1980. Comprehensive biochemical studies highlighted its broad substrate specificity for β-d-galacto-, gluco-, and fuco-sides and also showed its remarkable exo-glucosidase and transglycosidase activities. The enzyme demonstrated to be active and stable over a wide range of temperature and pHs, withstanding to several drastic conditions comprising solvents and detergents. Over the years, a great deal of studies were focused on its homotetrameric tridimensional structure, elucidating several structural features involved in the enzyme stability, such as ion pairs and post-translational modifications. Several β-glycosidase mutants were produced in the years in order to understand its peculiar behavior in extreme conditions and/or to improve its functional properties. The β-glycosidase overproduction was also afforded reporting numerous studies dealing with its production in the mesophilic host Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, and Lactococcus lactis. Relevant applications in food, beverages, bioenergy, pharmaceuticals, and nutraceutical fields of this enzyme, both in free and immobilized forms, highlighted its biotechnological relevance.

Sugar transport in Sulfolobus solfataricus is mediated by two families of binding protein-dependent ABC transporters

The extreme thermoacidophilic archaeon Sulfolobus solfataricus grows optimally at 80 degrees C and pH 3 and uses a variety of sugars as sole carbon and energy source. Glucose transport in this organism is mediated by a high-affinity binding protein-dependent ATP-binding cassette (ABC) transporter. Sugar-binding studies revealed the presence of four additional membrane-bound binding proteins for arabinose, cellobiose, maltose and trehalose. These glycosylated binding proteins are subunits of ABC transporters that fall into two distinct groups: (i) monosaccharide transporters that are homologous to the sugar transport family containing a single ATPase and a periplasmic-binding protein that is processed at an unusual site at its amino-terminus; (ii) di- and oligosaccharide transporters, which are homologous to the family of oligo/dipeptide transporters that contain two different ATPases, and a binding protein that is synthesized with a typical bacterial signal sequence. The latter family has not been implicated in sugar transport before. These data indicate that binding protein-dependent transport is the predominant mechanism of transport for sugars in S. solfataricus.

Hyperthermophilic enzymes: sources, uses, and molecular mechanisms for thermostability

Enzymes synthesized by hyperthermophiles (bacteria and archaea with optimal growth temperatures of > 80 degrees C), also called hyperthermophilic enzymes, are typically thermostable (i.e., resistant to irreversible inactivation at high temperatures) and are optimally active at high temperatures. These enzymes share the same catalytic mechanisms with their mesophilic counterparts. When cloned and expressed in mesophilic hosts, hyperthermophilic enzymes usually retain their thermal properties, indicating that these properties are genetically encoded. Sequence alignments, amino acid content comparisons, crystal structure comparisons, and mutagenesis experiments indicate that hyperthermophilic enzymes are, indeed, very similar to their mesophilic homologues. No single mechanism is responsible for the remarkable stability of hyperthermophilic enzymes. Increased thermostability must be found, instead, in a small number of highly specific alterations that often do not obey any obvious traffic rules. After briefly discussing the diversity of hyperthermophilic organisms, this review concentrates on the remarkable thermostability of their enzymes. The biochemical and molecular properties of hyperthermophilic enzymes are described. Mechanisms responsible for protein inactivation are reviewed. The molecular mechanisms involved in protein thermostabilization are discussed, including ion pairs, hydrogen bonds, hydrophobic interactions, disulfide bridges, packing, decrease of the entropy of unfolding, and intersubunit interactions. Finally, current uses and potential applications of thermophilic and hyperthermophilic enzymes as research reagents and as catalysts for industrial processes are described.

Intramolecular dynamics and conformational transition in proteins studied by biophysical labelling methods. Common and specific features of proteins from thermophylic micro-organisms

A general survey is carried out on the theoretical grounds for methods of spin, luminescence and Mössbauer labels, as well as their application in the study of protein intramolecular dynamics. When combined, these methods allow the protein dynamics to be investigated within a wide range of correlation times (tau c = 10(2) - 10(-10) s) and amplitudes. The purposeful application of the methods to various proteins at different temperatures (30-330 K), water content, substrate addition, etc., revealed a number of dynamical processes and conformational transitions in proteins. The experiments indicated correlations between the local segmental mobility of protein globules in a nanosecond temporal scale and biochemical reactions, such as long-distance electron transfer, hydrolysis and photoreactions. The biophysical labelling methods results were analysed together with the data on dynamics obtained using complementary physico-chemical methods and theoretical calculations. Special emphasis is given to recent results on proteins from thermophylic micro-organisms. The mechanisms of protein intramolecular dynamics and their role in the stability and functions of proteins and enzymes are discussed.

Pyruvate kinase from the thermophilic eubacterium Bacillus acidocaldarius as probe to monitor the sodium concentrations in the blood

We describe the isolation and characterization of a pyruvate kinase from the thermophilic eubacterium Bacillus acidocaldarius. This protein appears to be a tetramer composed of four 55-kDa subunits. The intrinsic tryptophan fluorescence of this protein is quenched by approximately 20% upon binding sodium, which occurs with a dissociation constant near 15 mM. Importantly, the intrinsic fluorescence of this pyruvate kinase does not appear to be affected by potassium, magnesium, and calcium at the concentrations found in whole blood. It appears that this pyruvate kinase can provide the basis for a selective protein sensor for sodium with minimal interference from other cations.

The beta-glycosidase from the hyperthermophilic archaeon Sulfolobus solfataricus: enzyme activity and conformational dynamics at temperatures above 100 degrees C

Enzymes from thermophilic organisms are stable and active at temperatures which rapidly denature mesophilic proteins. However, there is not yet a complete understanding of the structural basis of their thermostability and thermoactivity since for each protein there seems to exist special networks of interactions that make it stable under the desired conditions. Here we have investigated the activity and conformational dynamics above 100 degrees C of the beta-glycosidase isolated from the hyperthermophilic archaeon Sulfolobus solfataricus. This has been made possible using a special stainless steel optical pressure cell which allowed us to perform enzyme assays and fluorescence measurements up to 160 degrees C without boiling the sample. The beta-glycosidase from S. solfataricus showed maximal activity at 125 degrees C. The time-resolved fluorescence studies showed that the intrinsic tryptophanyl fluorescence emission of the protein was represented by a bimodal distribution with Lorential shape and that temperature strongly affected the protein conformational dynamics. Remarkably, the tryptophan emission reveals that the indolic residues remain shielded from the solvent even at 125 degrees C, as shown by shielding from quenching and restricted tryptophan solubility. The relationship between enzyme activity and protein structural dynamics is discussed.

Structure-function studies on beta-glycosidase from Sulfolobus solfataricus. Molecular bases of thermostability

beta-Glycosidase from the extreme thermophilic archaeon Sulfolobus solfataricus is a thermostable tetrameric protein with a molecular mass of 240 kDa which is stable in the presence of detergents and has a maximal activity above 95 degrees C. An understanding of the structure-function relationship of the enzyme under different chemical-physical conditions is of fundamental importance for both theoretical and application purposes. In this paper we report the effect of basic pH values on the structural stability of this enzyme. The structure of the enzyme was studied at pH 10 and in the temperature range 25-97.5 degrees C using circular dichroism, Fourier-transform infrared and fluorescence spectroscopy. The spectroscopic data indicated that the enzyme stability was strongly affected by pH 10 suggesting that the destabilization of the protein structure is correlated with the perturbation of ionic interactions present in the native protein at neutral pHs. These experiments give support to the observation derived from the 3D-structure, that large ion pair networks on the surface stabilize Sulfolobus solfataricus beta-glycosidase.